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20 Cards in this Set
- Front
- Back
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What is one EV defined as? |
The kinetic energy carried by an electron when it's a accelerated through a pd of 1v |
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How did Millikan calculate the charge of an oil drop? |
He made a oil drop fall without the electric field being switched on and then presumed that it would fall at its terminal velocity so he could say that the viscous force and the weight of the oil drop were equal to each other and he could rearrange this to get what r equaled. Next he turned the electric field and adjusted the voltage until the oil drop was stationary. He could then assume that the weight of the oil droplet and the electrostatic force on it were equal and then rearrange this to get Q by saying that mass equaled the volume × density |
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What did Millikan conclude from his oil drop experiment? |
That the charge he got was always a multiple of 1.6×10^19 which he presumed was the charge of an electron. This meant that charge is quantised and it only exists in packets of 1.6×10^19 |
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What did newton suggest about light? |
That light was made up of particles called corpuscles |
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What was newton's theory based on? |
On the laws of motion that copuscles would naturally travel in a straight line and back then light was only known to reflect and refract so he thought his theory explained why light didn't diffract like sound did so he thought that it wasn't a wave |
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How did Newton explain reflection and refraction with his theory? |
He thought that reflection was due to the force that pushed the particles away from the surface and refraction was because the particles travelled at a faster speed in a transparent substance and there was an attractive force activity perpendicular to the boundary which made them change direction in the substance |
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How was Newton's wave theory of light proven wrong? |
With youngs double slit since he showed that light showed diffraction and interference properties which are only properties of waves |
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What experiment proved Huygens wave theory wrong? |
The photoelectric effect |
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What three conclusions were drawn from the photoelectric effect experiment? |
1.No photoelectrons are emitted below a certain frequency known as the threshold frequency. 2.The photoelectrons had a range of kinetic energies ranging from 0 to a maximum value which increases with frequency and is unaffected by the intensity of the radiation 3.The number of photoelectrons emitted per second was directly proportional to the intensity of the radiation |
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Why did this prove the wave theory of light wrong? |
Because according to the wave theory of light energy is proprtional to the intensity and eventually each electron would gain enough energy to be able to leave the metal. So the result they were expecting was that the kinetic energy to increase with intensity and for frequency not to have an impact |
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What's a black body? |
It's a body which emits and absorbs all wavelengths of electromagnetic radiation |
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How does a transmission electron microscope work? |
By using a very thin sample it allows the electron beam to pass straight through it which makes an image which is projected onto a screen to form an image |
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How does a scanning tunnelling microscope work |
It has a very fine probe which is moved over the surface of the sample and a voltage is applied between the probe and the sample allowing electrons to flow between the probe and the sample which creates a very small current. The smaller the distance is between the surface and probe the bigger the current is which means that the information gained from changes in current allows you to create an image of the surface |
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What is absolute motion? |
It's when they thought everything including light moved relative to a fixed background |
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What was drawn from the experiment to measure the speed of the earth? |
There's no ether since it was impossible to detect absolute motion and the speed of light has the same value for all observers |
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What's a inertial reference frame? |
One in which newton's first law is obeyed |
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What assumptions are Einsteins theory of special relativity based on? |
Physical laws have the same form in all inertial frames and the speed of light in free space is invariant? |
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What does the speed of light in free space is invariant mean? |
That the speed of light always has the same value and isn't affected by the movement of the person measuring it or by the movement of the light source |
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State two conclusions that were drawn from Thomson experiments? |
1.Cathode rays were negativity charged particles 2.particle had a much smaller mass than that of an atom |
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Why couldn't the wave theory explain the threshold frequency? |
Because they thought that light of any frequency should cause photoelectric emissions. It predicted that the lower the frequency is the longer it will take the electron to gain enough energy but the electron would eventually gain enough to escape since it predicted that energy was constantly transferred to the electron |
