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132 Cards in this Set
- Front
- Back
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The molecules present within the colored object determine what? |
Which colors are reflected and which are absorbed. |
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White objects do what to all colors? |
Reflect all colors. |
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Black objects do what to all colors? |
Absorb all colors. |
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Colored objects do what to white light? |
Absorb some colors and reflect others. |
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What molecules make leaves and plants green? |
Chlorophylls |
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Chlorophylls absorb light of all colors except... |
Green, Blue, and some Yellow. |
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T/F In the fall, chemical reactions within leaves destroy the chlorophyll molecules, and a different class of molecules, called Carotenes, dominates the leaf's color. |
True |
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Carotenes are responsible for the color of which vegetable? |
Carrots |
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Carotenes absorb all colors except... |
Red and Orange. |
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T/F Light is matter and has mass. |
False, Light is not matter and has no mass. |
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What is the speed of light in meters/second? |
3.0 x 10^8 m/s |
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What is the speed of light in miles/second? |
186,000 miles/second |
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T/F Light and sound are formed at the same time, but the light reaches us much faster than the sound. |
True |
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One of the complexities of light is its duel nature, what are the two properties it shows? |
Wave properties and particle properties. |
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Particles of light are called what? |
Photons |
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T/F We can think of particles of light as tiny packets of energy traveling at the speed of light. |
True |
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During the day, how many photons enter our eyes every second? In the dark? |
Billions 10-20 |
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Human eyes are as sensitive to as few as ___ - ___ Photons, making them one of the most versatile photon detectors known.
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5 - 10 |
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The wave nature of light is embodied in which two fields? |
Magnetic and electric fields. |
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What is a magnetic field? |
The area around a magnet where forces are experienced. |
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What is an electric field? |
The area around a charged particle where forces are experienced. |
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T/F The wave nature of light is an oscillating wave of electric and magnetic fields. |
True |
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What is wavelength? |
The distance between wave crests. |
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Wavelength is represented by which Greek letter? |
𝝺
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𝝺 This symbol represents what? |
Wavelength |
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Wavelength determines what two things? |
Color of the light (type of light)
How much energy is in one of its photons. |
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Label each blank space. |
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The relationship between the wavelength and energy of light is what kind of relationship? |
An inverse relationship. |
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Draw the equation for the relationship between wavelength and energy of light. |
Ephoton is the energy carried by the photon. 𝝺 is the wavelength of light. ∝ means "proportional to." |
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The lasers used in supermarket scanners emit a red light at a wavelength of 633nm. Compact disc players use lasers that emit light (that is not visible) at 840 nm. Which photons - those emitted by the scanners or CD players - contain more energy per photon? |
The red light of the supermarket scanner has a shorter wavelength and therefore a higher energy per photon. |
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What is frequency? |
The frequency of light is the number of cycles or crests that pass through a stationary point in 1s. |
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What is the unit of frequency? |
1/s |
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What is another name for the unit of frequency? |
Hertz (Hz) |
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Frequency and wavelength have what kind of relationship? |
An inverse relationship. |
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T/F The shorter the wavelength, the higher the frequency. |
True |
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Frequency is represent by what? |
The greek letter "V" |
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Draw the equation you would use to find frequency. |
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Draw the equation you would use to find wavelength. |
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The speed of light is represented by what? |
The letter "c" |
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What does the letter "c" represent? |
The speed of light. |
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What does the letter "𝒱" represent? |
Frequency. |
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What does the letter "𝜆" represent? |
Wavelength. |
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Radio waves are a form of electromagnetic radiation with long wavelengths. Calculate the wavelength used to produce a FM radio signal that appears at 100.7 megahertz (MHz; mega = 10^6). |
3.00 x 10^8 m/s ----------------------- = 100.7 x 10^6 /s 2.98 m |
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List the symbol and factor related to the prefix Giga- |
G 10^9 |
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List the symbol and factor related to the prefix Mega- |
M 10^6 |
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List the symbol and factor related to the prefix kilo- |
k 10^3 |
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List the symbol and factor related to the prefix deci- |
d 10^ -1 |
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List the symbol and factor related to the prefix centi- |
c 10^ -2 |
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List the symbol and factor related to the prefix milli- |
m 10^ -3 |
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List the symbol and factor related to the prefix micro- |
µ 10^ -6 |
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List the symbol and factor related to the prefix nano- |
n 10^ -9 |
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Calculate the wavelength of electromagnetic radiation used to produce an AM radio signal that appears at 840 kHz. |
3.00 x 10^8 m/s ----------------------- = 840 x 10^3 /s 357 m |
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Which photons contain more energy, X-ray photons with a frequency of 3 x 10^17 Hz or ultraviolet photons with a frequency of 2 x 10^15 Hz? |
X-ray photons. |
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T/F The energy of a photon is directly proportional to its frequency. |
True |
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What is visible light? |
Light visible to the human eye. |
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What is the general term for all forms of light? |
Electromagnetic radiation |
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What is electromagnetic radiation? |
All forms of light, visible and non-visible. |
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Where does ultraviolet (UV) light fall on the electromagnetic spectrum? |
Between X-rays which have shorter wave lengths and visible, violet which has longer wavelengths. |
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T/F We can see UV light. |
False, it is invisible. |
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T/F Because of its shorter wavelength, its photons carry more energy than visible light. Consequently, UV light has enough energy in its photons to break chemical bonds and damage biological molecules. |
True |
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X-rays fall where on the electromagnetic spectrum? |
In-between gamma-rays and UV light. |
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Who discovered X-rays and when did he discover them? |
The German physicist Wilhelm Roentgen in 1895. |
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T/F X-rays are not harmful to biological tissues. |
False, X-rays are harmful to biological tissues. |
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The shortest of all wavelengths are what? What are they produced by? |
Gamma-rays. The sun and other objects in space. |
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T/F Because of their destructive ability, gamma rays are used in radiation therapy to irradiate and destroy cancerous tumors.
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True
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Where does infrared (IR) light fall on the electromagnetic spectrum? |
Between visible,red light and Microwaves. |
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What comes between IR light and Radio waves on the electromagnetic spectrum? |
Microwaves |
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Which are the longest wavelengths of the electromagnetic spectrum? |
Radio waves |
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Microwave energy is efficiently absorbed by what kinds of molecules? |
Water molecules |
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T/F Microwave radiation efficiently heats substances that contain water but does not affect substances that do not. |
True |
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Who discovered radio waves and when did he do it? |
Heinrich Hertz 1888 |
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What are four common things that use radio waves to transmit signals? |
Radio, AM & FM Cell phones television satellite links |
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T/F Light is not a form of energy. |
False, light is a form of energy. |
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A molecule or atom gains what upon the absorption of light? |
Energy
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What does it mean when electrons are excited? |
The electrons have captured energy and move from lower-energy orbits to higher-energy orbits. |
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The energy required to make an electron jump to a higher state can be provided by light if the energy of the photon does what? |
If the energy of the Photon exactly matches the energy required to move the electron from one orbit to the next. |
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The energy of the photon (which depends on its wavelength) must be ________ ________ to the ________ __________ between the two orbits. |
Exactly Equal Energy Difference |
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The electron configuration of a molecule or atom with electrons in particular orbits is called what? |
Energy state |
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What is the ground energy state? |
When all electrons are in the lowest-energy orbits possible. |
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Light causes an __________ ___________ from one energy state of the molecule or atom to another, higher-energy state. It does this by promoting an electron to a higher-energy orbit. When the electron is in the higher-energy orbit, the atom or molecule is said to be in an _________ ________. |
Electronic transition Excited state |
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After an electron in a molecule is excited to a higher-energy orbit with light, the molecule is left in what kind of excited state? |
An unstable excited state. |
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The excess energy from a molecule in an unstable excited state can be dissipated in what two ways? |
Photodecomposition
Electronic relaxation by the emission of light Electronic relaxation by the emission of heat |
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What is photodecomposition?
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When the energy from an absorbed photon is high enough to break the bonds within a molecule and potentially make the molecule fall apart. |
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What is electronic relaxation? |
When the electron falls back to its original orbit, producing either heat or light in the process. |
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The emission of light occurs in two ways, what are they? |
Phosphorescence Fluorescence |
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What is the difference between Phosphorescence and fluorescence? Which is faster? |
The time required for electrons to relax. Fluorescence happens fast. Phosphorescence happens slow. Fluorescing objects stop the instant they are removed from the energy source, whereas phosphorescing objects continue to glow. |
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What is an example of Phosphorescence? |
Glow-in-the-dark toys |
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What is an example of Fluorescence? |
The glow of a white T-shirt under black light (which emits UV light). |
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In summary, the excitation of electrons in molecules can result in _______________ - in which molecules break down to other substances - or ___________. ___________ can occur either through the ___________ of ________ or through the ___________ of ________. The _________ of __________ can occur either through _________________, a long-lived process, or through _______________, a short-lived process. |
Photodecompostion Relaxation Relaxation Emission of heat Emission of light Emission of light Phosphorescence Fluorescence |
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Complete this drawing. |
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Complete this drawing. |
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Complete this drawing. |
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T/F The specific wavelengths of light absorbed or emitted by a particular molecule or atom are unique to that molecule or atom and can be used to identify it. |
True |
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What is Spectroscopy? |
A technique in which the interaction of light with matter is used to identify unknown substances. |
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T/F Spectroscopy is one of the most versatile tools a scientist has at his or her disposal for identifying and quantifying matter. |
True |
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Complete the drawing. |
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List visible light in order of highest energy to lowest energy. |
Violet Blue Green Yellow Orange Red |
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List all electromagnetic radiation in order from highest-energy to lowest-energy. |
Gamma-rays X-rays UV light Violet Blue Green Yellow Orange Red Infrared light Microwaves FM Radio AM Radio |
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What does "MRI" stand for? |
Magnetic Resonance Imaging |
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The technology of MRI is based on what? |
The spectroscopy of hydrogen atoms in a magnetic field. |
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Why is the spectroscopy of hydrogen atoms in particular used in MRI? |
Because of the abundance of hydrogen atoms in the human body, in water and organic molecules. |
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T/F MRI involves the nuclei of hydrogen atoms and was originally called Nuclear Magnetic Resonance. |
True |
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Who developed MRI and when did they do it? |
Felix Bloch of Stanford and Edward Purcell of Harvard in the 1940's. |
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How does MRI work? |
AAA |
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What is relaxation time, in regards to MRI? |
The time required for nuclei to return to their original orientation after being pushed by electromagnetic radiation. |
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Is relaxation time, in regards to MRI, sensitive to the local environment of the hydrogen atoms? Why? |
Yes, because different biological tissues contain nuclei in different environments. MRI can distinguish between these types of tissue. |
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What are some things that lasers are used for? |
Visual effects As precision drills As aiming devices As invisible scalpels In Supermarket scanners In CD players In Laser printers In Surveying equipment |
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What does the acronym LASER stand for? |
Light Amplification by Stimulated Emission of Radiation. |
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What are the two differences between white light and laser light? |
1. White light contains many wave lengths, while laser light contains only one wavelength. 2. The differences in the alignment of electromagnetic waves. White light's waves are randomly oriented, while Laser's waves are aligned, or in phase. |
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T/F Because of the nature of a Laser, it is a very pure, intense form of light that does not spread much as it travels through space. |
True |
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Complete the Drawing about White light vs Laser light. |
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Excited state = ? |
Unstable |
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Ground state = ? |
Stable |
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Emission = ? |
Higher to lower |
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Absorption = ? |
Lower to higher |
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What is a node? |
It is a point along a standing wave where the wave has minimum amplitude. |
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The primary difference among lasers is the lasing medium. What are the four types of lasers? |
Solid-state lasers Gas lasers Dye lasers Semi-conductor (diode) lasers |
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What is the lasing medium in a solid-state laser? |
A metal ion distributed in a solid crystal. |
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What is the lasing medium in a gas laser? |
A gas or a mixture of gases contained in a tube. |
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What is the lasing medium in a Dye laser? |
An organic dye in a liquid solution. |
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What is the lasing medium in a Semiconductor (Diode) laser? |
Two semiconducting materials sandwiched together. |
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What are the three most common types of gas lasers? Which gas laser is the most powerful? |
Helium-neon Argon Carbon dioxide Carbon dioxide is the most powerful with the potential to cut through steel. |
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What is a lasing medium? |
Lasing mediums are the molecules or atoms that are being excited in order to produce light upon dissipation of excess energy through the emission of light. |
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What is a lasing cavity? |
The lasing cavity houses the lasing medium. It also contains a mirror and a partial reflector. The light in the lasing cavity will bounce back and forth causing a chain reaction that increases the number of photons in the cavity. A small fraction of photons leak out through a hole in the partial reflector. |
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Draw the components of a lasing cavity. |
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Characteristic Emission Wavelengths Hydrogen |
656 - Red 486 - Green 434 - Blue 410 - Violet |
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Characteristic Emission Wavelengths Helium |
706 - Red 587 - Yellow 502 - Green 447 - Blue |
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Characteristic Emission Wavelengths Lithium |
671 - Red |
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Characteristic Emission Wavelengths Sodium |
589 - Yellow |
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Characteristic Emission Wavelengths Mercury |
579 - Yellow 546 - Green 436 - Blue 405 - Violet |
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Amplitude ≈ ____________ |
Brightness |
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Every wave has four characteristics. What are they? |
Wave speed Amplitude Length Frequency |
