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212 Cards in this Set
- Front
- Back
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What is thermodynamics |
Study of heat transfer and the resulting temperature changes |
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What do we mean when we say that something has undergone a thermal interaction? |
Temperature of something changes |
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What do we mean by thermal equilibrium? |
Temperature of a system remains constant |
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Quantitiy that is related to the height of a column of liquid inside a familiar glass bulb thermometer |
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What does it mean when a thermometer is said to be calibrated |
If the length of the column is associated with standard temperature units and scales such as Fahrenheit or Celsius |
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How are temperature scales established |
By taking two "fixed points" that were reliable, easily reproducible temperatures associated with known physical situations |
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What is the triple point of water? |
Temperature and pressure at which solid ice, liquid water and water vapor can coexist |
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What is considered to be the fundamental scale in thermodynamics |
The Kelvin temperature scale |
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What is the equation to get between kelvin and celsius |
k = c + 273.15 |
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What is absolute zero |
0K, believed to be the lowest possible temperature |
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What must happen when you use an electronic temperature sensor in combination with a particular computer and interface? |
Must be calibrated against a glass bulb thermometer or ome other known standard |
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How many divisions does the celsius scale have? |
0C - 100 C = 100 divisions |
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How many divisions does the kelvin scale have |
273 K - 373 K = 100 divisions |
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How many divisions does the fahrenheit scale have? |
32 F - 212 F = 180 divisions |
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Which degree is larger between celsius, kelvin and fahrenheit? |
celsius and kelvin have larger degrees |
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When a nurse pops a room temperature glass bulb thermometer in your mouth to see if you have a fever, he leaves the thermometer in your mouth awhile before reading the temperature. Why does he wait? |
Because it takes a while for thermodynamic equilibirum to be reached between liquid in thermometer and mouth |
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Which reaches room temperature faster, a thermometer in room temperature water or one in air |
One in room temperature water |
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If you put two thermometers in hot water then dried one off while leaving the other one wet, which would reach room temperature faster? |
The wet one because of evaporative cooling, so as the water molecules vaporizes, it absorbs and takes away heat |
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What is an important point you need to remember when taking temperature measurments? |
It is important to wait until the temperature reading of the sensor remains fairly constant (until the temperature sensor and the object are in thermal equilibirum) |
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Hot objects cool down until the reach the same temperature as objects around them. True or false? |
True |
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Is the rate of temperature change faster in the beginning or at the end? |
Beginning, because there is a higher temperature difference between temperature of the water and air. A larger temeprature gradient leads to quicker rate of cooling (Rate of water cooling decreases greatly initially but as the temperature drops, the rate slow down until it tapers off at room temperautre) |
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If you had a mass of hot water at 80C in a small, sealed, uninsulated container and a larger mass of water at room termpature (20 C) in a cup. The container is submerged in the water in the cup and left there for a long time. Would the final temperature of the water in the container be midway between 80 and 20 C, or will it be closer to 80 C or 20 C |
Closer to 20 C but slightly higher |
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If you had a mass of hot water at 80C in a small, sealed, uninsulated container and a larger mass of water at room termpature (20 C) in a cup. The container is submerged in the water in the cup and left there for a long time. Would the final temperature of the water in the cup be midway between 80 and 20 C, or will it be closer to 80 C or 20 C |
Closer to 20 C because water in a cup is a larger mass so it takes more eergy to heat up than the samller mass |
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Is it possible knowing just the initital temperatures (and not the masses) of the water to predict exactly what the final temperature will be |
No, because initial temperature alone is not responsible for temperature change (would need to take mass into consideration) |
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How does the temperature change occur of a small, unisulated container of hot water being put into a cup of room temperature water |
The temperature change came form heat being transferred betwene the hot and room temperature water
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How can you tell if thermal equilibrium has been reached |
The final termpeature would be the same if thermal equilibirum has been reached, because no more heat energy transfer |
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If you transfer heat to water in a cup at the same rate as heat is transferred out, what will happen to the temeprature of the water? |
Stay the same |
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What woul happen if you transfer in more heat than is transferred out |
Temperature will increase |
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What will happen if you transfer less heat to water in a cup than heat is transferred out, what will happen to the tmeperature |
Temperature will decrease |
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What is temperature change directly proportional to? |
Amount of heat added |
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What factor besides temperature change might determien the amount of heat transfer that was needed |
Mass |
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What type of relationship exists between the temperature of the water and quantiity of heat transferred |
Linear A higher quantity of heat transfrred made the temperature of the water increase |
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If you doubled the mass of water and transferred the same amount of heat, what would happen to the tmeperature change |
The temperature would decrease by a factor of two
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Why must a thermometer be calibrated |
A thermometer must be calibrated to get accurate measurements |
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You have a glass bulb thermometer with no markings on it and a second one marked in degrees Celsius. Explain how you would calibrate the unmarked thermometer |
Will calibrate the unmarked thermometer by putting both the marked thermometer in ice water ot make sure its o C as well as the unmarked thermometer in ice water to know where 0C is ion the unmarked one. Do the same of boiling water (100C) and then make marks between the two |
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Compare the length of time it takes the temperature sensor to reach thermal equilibirum with the air or water it is in. Is it easier to exchange heat between a thermometer and air or between a thermometer and water. |
It is easier to exchange heat between a thermometer and water, so it takes less time to reach thermal equilibrium. It is easier to exchange heat between a thermometer and water, because air is a better insulator and so doesn't exchange heat as fast |
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Why does evaporation make your body feel cooler |
Heat is needed to trun the fluid to vapor on your skin, therefore, heat is taken out of the object, making it feel cooler as the fluid goes into the surrounding |
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Between a cup of hot chocolate being cooled down to room temperature (25 C) and outside (5 C) which one will have the larger initial rate of cooling |
5 C Is larger because there is a larger temperature different and gradient so the rate is faster initially |
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When a cup of hot chocolate is cooling down where does the heat go |
Into the air, cup and surroundings |
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You have a mass of hot water at 90 C and twice the mass of cool wter at 10 C. The hot and cold water are mixed together. Will the final temperature be midway between 10 and 90C, closer to 90 C or closer to 10 C? Explain your reasoning |
Closer to 10 C bcause it takes more energy to heat twice as much mass, terefore the cooler temperature would increase less than the smaller mass. Because the heat given off by the hot water has to equal he that is absorbed by the cooler water |
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Define thermal equilibirum |
Two physical systems are in thermal equilibirum if no heat flows between them (no heat exchanges) |
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How can you tell that two objects are in thermal equilbiirum when they are in thermal contact |
If the temperature doesn't change when you allow a path permeable to heat between them |
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How is it possible to transfer different amounts of heat to each container and get the same temperature change |
Because temperature and mass are inversely proportional so a bigger mass requires more heat energy to get to the same temperature change |
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What is heat? |
A form of energy That flows when there is a temperature difference between two object |
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The common unit of heat energy is what |
Calorie |
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What is the mechanical equivalent of heat |
Number that converts calories into joules |
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Why does nail feel warmer when rub it on emery paper |
Evidence of mechanical work being done while rubbing took place because the friction is expressed as heat |
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By rubbing with the same force over the same length, should the rate of doing work (the power) be constant? |
Yes |
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Total work done in rubbing the metal on the emery paper is proportional to what |
Time interval for rubbing (IE if rub for twice as long, do twice as much work) |
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What is the relationship between the work done and the temperature change? |
Linear relationship between the two (mechanical work energy and temperature change) Mechanical work energy can be converted into heat energy |
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When we were rubbing the metal against the emergy paper, why not hold the metal directly instead of using the foam insulation |
Because metal is a good conductor, so it would take heat from our hands and change the overall temperature change we see |
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What is heat energy |
Energy is transit between two systems in thermal contact due to temperature difference only, with the hotter system losing heat energy and the cooler system gains it (This is heat energy transfer) |
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How are two objects in thermal equilibirum |
Same temperature No energy on average is exchanged between them when they are placed in thermal contact |
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Does the electrical power output of the generator increase or derease as the crank is turned faster |
Increases |
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What does the generator do |
Changes mechanical energy into electrical energy |
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Is there a relationship between the temeprature change and the electrical energy generated by cranking the generator |
A linear relationship As electrical energy increases from interval of time cranking temperature increase (Final result is heat transfer) |
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How does the change in temeprature appear to depend on the amount of heat energy transfered to a fixed mass of water |
The amount of heat energy transferred is propprtional to the change in temeprature |
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Does the temperature change produced by one pulse depend on how warm the water is |
No, each pulse raises the temperature about the same amount each time |
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Is the change of temperature proportional or inversely proptional to the amount of heat energy transferred |
Proportional |
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Is the change in temperature proportional or inversely proportional to the mass of the system |
Inversely proportional |
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What is the specific heat of the material |
The amount of heat energy transfer that will produce a one degree change in temperature in unit mass of a material |
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How is it possible that rubbing a piece of metal on emery paper can result in an increase in the temperature of the metal? How is it possible that running an electric curent through a piece of metal can result in an increase in temperature? In each case, what is being transferred to the metal?
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Rubbing metal on emergy paper can result in a rise in temperature because mechanical work of the motion results in friction by rubbign which can help to increase heat trasnferred to the metal and raise the temperature. Running an electrical current works in a simialr fashion, electrical work and energy is transformed into heat, increasing the temperature of the metal |
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How did we figureo ut that heat is antoehr form of energy and the evidence that we foudn that heat is not a substance that flows from a hotter body to a colder one |
Heat is another form of energy which can be concluded through testing for changes in temperature as a function of how much work was done to a system. We figured out that heat is not a substance that flows from a hotter body to a colder one because heat was able to be generated from the objects of which they are the same temperature. This was found by the nail against the emery paper. Heat is special because it indicates a transfer of energy from one object to another |
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If you transfer heat energy to a perfectly insulated cup of some liquid, what determines how much the temperature changes |
Amount of heat transferred Mass of liquid Specific capacity |
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Will the total change in temperature be larger, smaller or the same when you transfer more heat energy |
Larger Because they are directly proportional |
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Will the total change in temperature be larger, smaller or the same when you heat for a longer time but transfer the same total heat energy |
Stay the same Only q is affected and not time so will remain the same |
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Will the total change in temperature be larger, smaller or the same when you start with more liquid in the cup |
Decrease Mass and delta T are inversely proportional so leads to less temperature change |
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Will the total change in temperature be larger, smaller or the same when you increase the starting temperature of the liquid |
Same Same total amoutn of heat energy added, it will ahve the same delta t just a higher final temperature |
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Will the total change in temperature be larger, smaller or the same when you use an equal mass of liquid that has a larger specific heat |
Less Because c and delta A are inversely proporational |
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Will the total change in temperature be larger, smaller or the same when you use a same volume of a dense liquid with the same specific heat |
Less Mass increased, two are inversely proportional |
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How many calories of heat would it take to heat 200 mL of water from 20 to 80 C? |
12 000 Cal (HW 2) |
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Comapre the heat energy needed to heat 200 mL of water from 20 to 80 C to that needed to heat 100 mL of water from 90 to 90 C |
3 000 Cal (HW 2) |
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How long would it take to heat the water of 200 mL from 20 to 80 C using a heater with a power rating of 50 W |
1005.6 c (HW 2) |
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A piece of aluminum (c = 910 J/Kg*C) of mass 200 g at 80 C is dropped into an unsulated cup filled with 100 mL of water at 20 C. What are the final temperatures of the water and aluminum |
38.2 C (HW 2) |
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Describe the relationship between the rate of heat energy transfer to keep the water at its initial temperature and difference in temperature based on your data? |
Rate of heat energy transfer is proportional to the difference in temperature. The larger the initial temperature with respect to room temperature, the larger the number of pulses required |
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The temperature inside a house is kept at a constant 20 C. Compare the cost of heating the house on a spring day when it is 10 C outside to that of heating the hosue on a winter day when it is -10 C outside. |
Cost 3x more when its -10 C outside than when it's 10 C because the difference betwene thetemperature of the water and room temperature is larger when it's -10 C outside |
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Which mode of heat energy transfer (conduction or convection) is most affected by: covering the container?
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Convection |
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Which mode of heat energy transfer (conduction or convection) is most affected by: substituting foam for metal? |
Conduction |
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Which mode of heat energy transfer (conduction or convection) is most affected by: doublign the thickness of the foam |
Conduction |
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Is your sense of touch an accurate predictor of relative temepratures? |
No |
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Why do some objects feel colder than others even though they are the same temperature |
When you touch an object that is at room temperature, the thermal equilbiirum point would be reset because your body is never in thermal equilibirum with the room temeprature so it transfers heat |
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Between a shiny metal can and dull black painted can, which cup has the smaller change in temperature |
Covered shiny metal cup |
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Does radiation from the heat lamp transfer at a faster rate to a black metal can or shiny one |
Black |
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Black vs shiny surface talk about effectiveness at emitting and absorbing radiation. |
The black surface is effective at emitting radiation, since it is a good radiator, can also absorb more light which can be covnerted to heat energy |
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Which of the following seems to most accurately predict how fast heat energy is transferred from a hotter to a colder object? A) The temperature of the hotter object B) The temperature of the colder object C) The difference in temperature between the wo objects |
C The samples iwth a higher difference in temperature between system and surroundings required a faster rate of energy addition as compared to systems with smaller differences in temperature |
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The air temperature outside on a winter day is 10 C. Two identical outdoor swimming pools are heated by electric heaters. Swimming pool A is maintained by 20 C, while pool B is maintained at 30 C. Compared the rate at which heat energy is transferred to pool A with the rate at which heat energy is transferred to pool A. |
Heat energy will be transferred to pool B faster than pool A because larger temperature difference of 2 times. |
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Room temperature is 20 C. For what temperature of an object will there be no net heat energy transfer from the object tot he room or from the orom to the object. |
If the object is at 20 C in equilibirum with the room temerature then there will be no energy transfer. This is because the difference in temperature of the object and its surroundings is zero. |
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If objects sitting in a room for a long time are all at the same temperature, why do metal objects feel cooler to the touch than cloth or plastic ones? |
Metal objects feel cooler to the touch than cloth or plastic ones because metals are good conductors. When you're warmer than room temeprature and your hand touches the metal, the metal absorbs that heat much faster than cloth or plastic, making it feel cooler |
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What is conduction
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Transfer of heat via physical contact with a second object |
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What is convection
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Transfer of heat through a fluid via a transfer to gas or liquid |
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What is radiation |
Transfer of heat through light energy and by a hot surface |
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Which of the following changes is most effective in reducing heat energy transfer from a container of hot water and whihc is least effective? A) Replacing a metal can with a black surface with one with a shiny surface B) Replacing a metal can with a foam cup C) Replacing a single foam cup with two nested foam cups D) Putting a thin pastic cover on an open cup E) Replacing a thin plastic cover with a foam cover |
The most effective is replacing a thin plastic cover with a foam cover. We saw that foam is a good insulator and helps to keep heat in and covers were the most helful in decreasing the cooling rate. The least effective would be replacing a metal can with black surface. There was the smallest temeprature difference betwen the two. |
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For these: A) Replacing a metal can with a black surface with one with a shiny surface B) Replacing a metal can with a foam cup C) Replacing a single foam cup with two nested foam cups D) Putting a thin pastic cover on an open cup E) Replacing a thin plastic cover with a foam cover What will most affect conduction? |
Replacing a metal cup with foam cup Because it has to do with the transfer of heat from the water to the cup through physical contact |
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Between these: A) Replacing a metal can with a black surface with one with a shiny surface B) Replacing a metal can with a foam cup C) Replacing a single foam cup with two nested foam cups D) Putting a thin pastic cover on an open cup E) Replacing a thin plastic cover with a foam cover What will most affect convection |
D Because the addition of a lid helps prevent the heat loss to the air above the cup as well as minimize evaporation |
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Out of these: A) Replacing a metal can with a black surface with one with a shiny surface B) Replacing a metal can with a foam cup C) Replacing a single foam cup with two nested foam cups D) Putting a thin pastic cover on an open cup E) Replacing a thin plastic cover with a foam cover Which one is most affected by radiation |
A Because heat transfer of the other types are constant while the paint changes the emissivity of the cup |
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Out of the three differnet heat energy transfer processes ( conduction, convection and radiation) the most important in the cooling of an uncovered, uninsulated cup of hot water was? |
Convection, becuase it raised the largest temperature change when the cup was not covered |
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Assuming the roofing material has the same emission and absorption properties for visible and infrared radiation, would you choose a dark- or light- colored roof if you lived in a climate that is (a) warm and very sunny all year round and (b) cold and cloudy for much of the year |
(a) light colored roof so that it would refelect all the light and minimize heat transfer into the house B) Light colored roof so that it would prevent heat loss from inside the house by radiation |
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A thermos bottle has the following features to control transfer of heat energy in and out: (a) a tight cover, (b) a shiny metallic outside coating and (c) an air layer between the inside and outside surfaces. What function does each of these features seve in controlling heat energy transfer? That is, which of the heat transfer processes is most reduced by each design feature of the Thermos? |
A) Tight cover helps prevent the convectional losss of heat by minimizing exposure to the surrounding air B) Shiny metallic outside coating helps to reduce heat loss by radiation C) Air between the inside and outside layer acts as an extra layer of insulation, prevents conductive heat loss |
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In thermodynamics, why is pressure often a more useful quantitiy than force alone |
Because it is independent of the cross-sectional area of the cylinder |
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What is the equation of pressure |
Component of force that is perpendicular to a given surface per unit area of that surface P = F/A |
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Based on your observations of the two pistons, does the force or the pressure applied to one syrince get transmitted ot the other? |
The pressure applied to one syringe does seem to transmitted to one another because the forces are not the same; however, pressure is relatively similar on both sides |
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Why is pressure a more useful concept than force for a gas in a cylinder |
Because a gas doesn't have surface area, so it's easier to use pressure and volume rather than calculating force |
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What is the equation to work |
P(change in volume) |
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What is the equation for potential energy |
U = mgy u = -work |
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What is internal energy |
Any way of storing energy inside a system Sum of all sots of energies |
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What is the equation for the first law of thermodynamics |
U = Q -W |
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What are different ways of achieving the same change in internal energy |
Transfer large amount of heat energy to system and allow gas to do work on its surroudings Transfer a small amount of heat energy to the gas and not let it do any work at all |
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What is a situation where W is negligable and delta U = Q
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In any isovolumetric process where the volume is held constant such as a hot tub |
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How could you arrange a situation where Q is negligible and in which delta U = - W |
Adiabatic process So quickly no heat transfer, IE precessing a piston so quickly no heat exchange occurs |
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As you compress the air in a syringe by pushing the piston in slowly, so that the temeprature remains constnat what will happen to the pressure? What do you think will be the mathematical relationship between pressure P and volume V?
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As the air in the syringe is compressed at a constant temp, the volume decreased which the pressure increase (P is proportionla to 1/V) |
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Is P and V proportional or inversely proportional |
Inversly proportional |
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What is the relationship between P and T
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Linearly proportional (Guy Lussac's Law) |
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What is the relationship between V and T |
Linearly proportional (Charles' Law) |
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What happens to the velocity componenets when a collision with a wall takes palce? What is the change in the componenet of momentum perpendicular to the wall, produced by a collision |
Velocity becoems zero and back to its original velocity with a different direction with a collision with a wall. For example, for a delta p perpendicular to the wall, vx or vy changes 90 degrees for the initial hit. For example, hit one the side of the x wall, px=o and py will change direction |
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Does a wall exert a force on the molecule during a collison? How is this related to the rate of change of momentum of the molecule? Does the molecule exert a force on the wall |
Wall exert a force on the molecule as much as the molecule exerts a force on the wall. The rate of change of momentum equals forces exerted on the wall. (force = pressure/time) |
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What happened to the number of collisions per unit time with the piston as it is pushed in? What happens to the rate of change of momentum of the particles in these collisions? what should happen to the pressure (force per unit area) |
The number of collisions per unit time increased when the piston was pushed in because it was a smaller volume. Therefore, the pressure also increased since they are moving faster. P=m(delta v) therefore, pressure should increase as well since increased momentum leads to increased force with eads to increased pressure |
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Gas is in a cylinder sealed with a piston. If you push down quickly on the piston and ocmpress the gas, is work done on or by the gas? What happens to thei nternal energy of the gas? What happens to the temeprature of the gas |
Work = - (work done on gas) Internal energy increase because heat doesn't have tiem to be transferred so the process is adiabatic and Q = 0. Internal energy increases so temperature increases |
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Now you transfer heat energy to the gas in the cylinder, but hold the piston so it cannot move. Is work done on or by the gas? What happens to the internal energy of the gas? What happens to the tmeperature of the gas |
W = 0 Q = + U = + Tempertaure increases |
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After holding the piston in question 10 for a short while, you let it go. What happens to the piston? Is work done one or by the gas? What happens to the internal energy of the gas? What happens to the temperature of the gas? |
That piston will shoot up and the volume increases. Work is done by the gas on the surroundings. Since work is positive at constant Q, internal energy woudl decrease and so will the temperature. |
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What does boyle's law say? |
Pressure and volume are inversely related |
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What does Gay-Lussac's Law say |
Temperature and pressure are proportional |
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What does Charles' law say? |
Temperature and volume are proportional |
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Explain the origin of pressureo f a gas in a contianer basedo n the motions of molecules in the gas, their average momentum, and their collisions with the walls of the container |
Pressure results from collisions of molecuels against their container. Thus the faster the molecules move, the more frequent collisions with contianer there are and the greater their change in momentum (p = m (volume)) which leads to greater foce on the walls (F = change of momentum/time) and causes the pressure to increase (P= F/A) |
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Based on the kinetic theory defintion of temperature as the average kinetic energy of a molecule in an idea gas and your answer to Question 8, explain why the pressure of a gas increases when it is compressed while kept at a constant temperature |
Even though temperature is constant, the surface areas decreases for smaller containers. Thus, more frequent collisions with the container occurs whihc results in higher pressure |
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Based on the kinetic theory defintion of temperature as the average kinetic energy of a molecule in an ideal gas and your answer to Question 8, explain why the pressure of a gas increases when its tempreature is increased while the volume is kept constant |
The pressure of gas increases when its temperature is increased because that increases the average kinetic energy, which increases momentum with more frequent collisions, increases force on walls and increases pressure. |
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What is the basic goal of any heat engine |
Convert heat energy into work as efficiently as possible |
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What is a working medium |
Some substance that can expand or contract and thus do work when heat energy is transferred to it |
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What does a 100% efficient heat engine mean |
Working medium that transforms all of the heat energy transferred to it to useful work |
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What is a common statmeent of the second law |
It is impossible to transform all of the heat energy transferred to a system into useful work |
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Boyle's Law, the relationship between P and V in process is _____ constant |
T (Isothermal) You can accomplish this by changing the volume of the gas in a syringe very slowly so that the temperature of the gas had time to remain in thermal equilibirum with its surroundings-the air in the lab |
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If you compress a gas very quickly or the gas was in a cylinder that was well insulated from its surroundings, what type of process |
Adiabatic No heat energy is transferred to or from the gas during the process |
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What is the equation for the final temperature of diatomic ideal gas |
(final temperature)^2.5 (final volume) = (initial temperature)^2.5 (initial volume) |
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Why didn't the tissue paper catch fire when you compressed the air slowly |
Because slow compression gives enough time for the heat to equilibrate and heat is able to escape so no combustion occurs |
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How can you find work on a pressure vs volume graph |
area under the curve |
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If the gas expands, is the work positive or negative |
Positive |
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If the gas compressed, is the work positive or negative |
Negative |
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What is an equation for work in terms of QH and QC? |
W = QH - QC (QH = heat in) (Heat transferred to it, does work and transfers some of the original heat energy to the lower temperature surroundings) |
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When gas is expanding is it doing work on the surroundings or is work being done on the gas? |
Doing work on surorundings |
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When gas is compressed, is it doing work on the surroundings or is work beng done on the gas? |
Done on the gas by the surroundings (negative work) |
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Typically, at the completion of a heat engine cycle, does the gas have the same internal energy, temperature, pressure and volume that it started with? |
Yes |
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Why should the lifting and lowering parts of the cycle be isobaric |
Since the pressure in the air trapped in the syringe is determined yb the weight of the piston (and the mas on top of the handle) pushing down on the gas |
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Why is it when mass is added and removed from the piston handle, the processi s adiabatic/ |
Because it occurs very quickly |
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What happens if you add mass to a platform? |
Platform lowered, adiabatic |
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What happens when you put flask in the hot reservoir |
Platform rose, this is isobaric |
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What happens when you remove mass from platform? |
Platform raises up, adiabatic |
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What happens when you place the flask in cold reservoir |
Platform decreases, isobaricH |
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How do you calculate efficiency of a heat engine? |
e = 100% (W/QH) |
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How do you find heat energy transfer during an isobaric process |
Q = n(Cp) (delta T) |
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How do you find maximum (Carnot) efficiency |
ec = 100% (1-TC/TH) Both temps are in K |
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If 5 moles of air is at 0 C and 1 atm pressure (otherwise known as standard temperature and pressure, or STP for short), what is the volume occupid by the gas in m^3 |
0.113 m^3 (Homework 6) |
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Suppose that the gas in Question 1 is compressed isothermally until its volume is one-fifth as large. What is the final pressure? What is the final temperature? |
P = 5 atm Tf = 273 K (Homework 6) |
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The air in Question 1 is instead compressed adiabatically until its volume is one-fifth as large. Waht is the final temperature? What is the final pressure |
Tf = 520 K Pf= 9.52 atm |
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The air in question 1 is compressed isobarically until its volume is one-fifth as large. |
-90.4 J |
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What are rays and how are they used to represent light? |
Rays are identical focused beams of light that travel in straight line |
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Give two examples of light sources best represented by diverging rays |
Light bulb or street lamp |
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Give two examples of of light sources best represented by parallel rays |
Laser pointer Distent light source |
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The intensity at a distance of 5 cm from a point source of light is 25 watts/m^2. What is the intensity at the distance of 2.5 cm from the source? 15 cm from source? |
Because 5 to 2.5 is half the distance, 1/ (1/2)^2 is four times the intensity so at 2.5 cm, there is 100 w/m^2 intensity. At 15 cm, 1/(3^2) = 1/9 the intensity, so at 15 cm, intensity is 2.78 w/m^2 |
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Compare the change in light intensity with distance from a point source to the change for a source of plane waves (parallel rays). In which case is the change faster? Explain. |
Intensity from a point source will decrease slower than intensity from plane waves because they are a over which that light energy is dispersed increases a lot faster for plane waves than the point source.W |
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When you look at a photograph, where does the light taht reaches your eye originate? |
The light originate from the surroundings (light in the house, sun, etc). The light is then reflected off the picture which is what allows us to see it |
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You have a small frosted light bulb. There is a nonreflecting surface behind the bulb. The bulb is turned on. Describe how the light intensity varies as you mov further and further from the light bulb |
Light intensity will decrease by the proportion of I proportional to 1/R^2 as you move further away (it is the distance from light bulb) |
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You have a small frosted light bulb. There is a nonreflecting surface behind the bulb. Now the bulb is turned off, but light from a lamp is shined onto it. Describe similarities and differences from (a) in the way the light intensity varies as you move further and further away from the bulb. |
When very clsoe to the bulb, the intensity will decrease as proportion. However, at a certain distance, it will produce constant intensity expected from a point source. This light is being reflected only by a small point surrounded by non reflecting background that light is more focused |
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What is the relationship between intensity and distance of light |
As the distance of the light filament increases, the intensity decreased (Light power is the same but the surface area increases as the distance increases, so intensity decreases) |
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Why does chalk make laser beam more visible
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It is reflecting the laser beam H |
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How does light from laser appear differnet from the light from small light bulb |
Laser is a straight line while the bulb radiates. The laser's pathway is visible while the light bulb's pathway is not |
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When liht from a very distant source of light is incident on a relatively small object, is it best represented by approximately parallel rays (and plane waves) or by diverging rays and spherical waves |
Parallel |
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Does brighter object also have higher intensity |
Yes |
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Do objects like your body or the table top emit visible light? How can you see objects that are not soures of light? Where does the light come from |
Light comes form sun and light bulb Objects relfect light and that's how we see |
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What are rays like when they leave a source then hit a lens |
Rays are diverging and when hit lens are converging |
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For the lens, was the image of the arrow upright or inverted? |
Inverted |
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For the lens, was the image enlarged or reduced |
Enlarged |
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If mov the lens further away, what would happen to image |
Reduc in size |
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If move the lens closer, what would happen to image |
Larger |
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Carefully describe the function of a lens in forming an image. Describe what the lens does to the light coming from each point on the object |
A lens allows reflection of light, so light is reflected o nthe paper by passing throughout the lens and creates a virtual image |
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What kind of bulge does a double convex lens have |
Lens with both faces bulging out at the center |
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What does converging lens do with rays |
Bends rays so thta they converge and intersect at the point where the image is formed |
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What is the image point? |
Point where the image is force |
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What is the object distance? |
Distance from an object to the lens |
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What is the image distance |
Distance from the lens to the location of the image
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If the object is very distant from the lens what is the image point also called |
The focal point (Image distance would therefore be the focal length) |
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What is the focal length |
Number that characterizes how effective a lens is in focusing light rays |
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Does a smaller focal length'd lens have more or less buldge |
More Greater curvature, bends light more, so smaller focal length |
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If an object is not very distant will the image distance still be at the focal length? |
No, it will be past it (because rays no longer come in parallel) |
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How do you find magnification |
image size/object size |
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What happens to image size when the object distance is made smaller and smaller? What happens to the magnification? |
Larger and larger, until it disappears, magnification increases |
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What simple optical device uses converging lens |
Magnifying glass |
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Does diverging lens form virtual or real image |
Virtual |
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A camera has a lens (or combination of lenses) like the converging lens in this lab that focuses light from objects forming real images on a piece of film (like the screen in this lab). An enlarger shines light through a negative and uses a lens to project a real image of the picture on the negative onto the platform where the photographic paper is placed. Explain how each of the following will affect your photographs. Half of the lens on your camera is covered by a piece of paper |
Full image shown Just dinner |
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A camera has a lens (or combination of lenses) like the converging lens in this lab that focuses light from objects forming real images on a piece of film (like the screen in this lab). An enlarger shines light through a negative and uses a lens to project a real image of the picture on the negative onto the platform where the photographic paper is placed. Explain how each of the following will affect your photographs. The negative is placed in the enlarger with half of it covered by a piece of tape on the inside |
Only half of the real image will show up |
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A camera has a lens (or combination of lenses) like the converging lens in this lab that focuses light from objects forming real images on a piece of film (like the screen in this lab). An enlarger shines light through a negative and uses a lens to project a real image of the picture on the negative onto the platform where the photographic paper is placed. Explain how each of the following will affect your photographs. Half of the lens on the enlarger is covered by a piece of paper |
Full image shown Just dimmer |
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A camera has a lens (or combination of lenses) like the converging lens in this lab that focuses light from objects forming real images on a piece of film (like the screen in this lab). An enlarger shines light through a negative and uses a lens to project a real image of the picture on the negative onto the platform where the photographic paper is placed. Explain how each of the following will affect your photographs. The camera lens is replaced by a diverging lens with the same focal length |
No real image |
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You have a converging lens of focal length 20 cm. Answer the following based on your observations in this lab. For waht range of object distances will thei mage be larger than the object |
0-40 cm |
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You have a converging lens of focal length 20 cm. Answer the following based on your observations in this lab. For what range of object distances wil thei mage be smaller than the object |
> 40 cm |
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You have a converging lens of focal length 20 cm. Answer the following based on your observations in this lab. For what range of object distances will the image be upright |
< 20 cm |
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You have a converging lens of focal length 20 cm. Answer the following based on your observations in this lab. For what range of object distances will thei mage be inverted |
> 20 cm |
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You have a converging lens of focal length 20 cm. Answer the following based on your observations in this lab. For what range of object distances will the image be real |
>20 cm |
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You have a converging lens of focal length 20 cm. Answer the following based on your observations in this lab. For what range of object distances will image be virtual? |
Less than 20 cm |
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You have a diverging lens of focal length -20 cm. Answer the following based on your observations in this lab For what range of object distances will the image be larger than the object |
No range |
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You have a diverging lens of focal length -20 cm. Answer the following based on your observations in this lab For what range of object distances will the image be smaller than the object? |
All distances |
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You have a diverging lens of focal length -20 cm. Answer the following based on your observations in this lab For what range of object distances will thei mae be upright? |
All |
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You have a diverging lens of focal length -20 cm. Answer the following based on your observations in this lab For what range of object distances will the image be inverted? |
None |
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You have a diverging lens of focal length -20 cm. Answer the following based on your observations in this lab For what range of object distances will thei mage be real |
None |
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You have a diverging lens of focal length -20 cm. Answer the following based on your observations in this lab For what range of object distances will the image ve virtual |
All |
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What is interference |
When a light wave is separated into two or more parts (IE pasing through two small parallel slits) and the parts are later brought together |
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What is diffraction |
When extended light waves are blocked or restricted by a single object or slit Interfereance takes place between waves originating from different points of the same wave foront |
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You will first observe what happens when light passes through a single slit. To begin with, try a slit that is very large compared to the wavelength of light. A common, red. helium-neon laser emits light with wavelength 632.8 nm. How many wavelengths of a helium-neon laser are equivalent are 1.0 mm? Show your calculation |
(1*10^-3 m)/(632.8*10^-9 m ) = 1580.3 wavelengths |
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Is the diffraction pattern wider or narrower for the narrower slit? Explain based on your observations |
Wider |
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How does changing the spacing between the slits affect the observed interference pattern |
Changes the small peaks |
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Light from a helium-neon laser is shined on a slit of width 0.02 mm. Describe qualitatively the pattern of light seen on a screen 1.0 meter away |
Be a bright center and other dots of lights that are less bright than central peak. Further from center, less bright. |
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How would the pattern in (2) be different if the slit were 0.06 mm wide in stead of 0.02 mm? |
All of the fringes would be narrower, and envelope would be closer |
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How would the pattern (2) be different if instead of one slit there were two slits each 0.02 mm wide, separated by 0.2 mm |
The envelope would still be the same. However, there would be multiple small peaks for each big peak because there is superimposing of interference patterns from the two slits on the diffracting pattern on the single slit pattenr |
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How would pattern in (4) be different if there were two slits, each 0.02 mm wide, separated 0.4 mm? |
The small fringes would be narrower |
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Hwo does the width of the slits affect the intensity pattern of a two-slit interference pattern? |
Width of slit correspond to how far apart each primary fringe is from the nxt one. They affect the envelopeo f the patter. So a wider slit would result in a narrower envelope but higher intensity |
