# Shared Flashcard Set

## Details

Light and Color Midterm 1
Light and Color Midterm 1
43
Physics
04/25/2012

Term
 What is the speed of light?
Definition
 o   Nothing travels faster than light, 186,000 miles/second
Term
 What is a wave?
Definition
 o   A wave is a propagating disturbance through a medium
Term
 What happens when 2 waves meet?
Definition
 Constructive interference:2 waves meet, make a bigger wave, and continue on their way
Term
 What is destructive interference?
Definition
 Opposite crest and trough cancel out
Term
 What does in phase mean? Light/dark?
Definition
 It is constructive, they match up and make a bigger wave and is light
Term
 What does out of phase mean?
Definition
 They are opposite and cancel eachother out and is dark
Term
 In terms of amplitude, what is bright, dim, and no light?
Definition
 Large amplitude =bright Low amplitude=dim zero amplitude=no light
Term
 What is wavelength
Definition
 distance between two successive peaks
Term
 What is frequency?
Definition
 Number of peaks passing per second.
Term
 Large frequency=?
Definition
 Small wavelenths
Term
 How do you find the speed of a wave?
Definition
 Speed = wavelength x frequency
Term
 What is the fastest traveling EM wave?
Definition
 They all travel at the same speed but have different wavelengths
Term
 What is the progression of wave lengths for EM waves?
Definition
Term
 What is resonant frequency? What happens?
Definition
 The frequency in which they like to be shaken. If the wave shakes the object at its resonant frequency than it absorbs that energy
Term
 What happens when it is on resonance? Off resonance?
Definition
 On resonance- wave absorbed Off resonance- wave transmitted
Term
 What can you use gamma rays for?
Definition
 o   borderline protection(looking for nuclear things), see blood flow, nuclear explosions, sendoff rockets(could)
Term
 What can you use xrays for?
Definition
 o   Xrays: on resonance with skin off resonance with bone so you can see bone not skin, CAT Scan, see teeth(on resonance), see tumors, see black holes, tell where ozone is
Term
 What can you do with UV rays?
Definition
 o   Ultra-violet: skin is on-resonance (waves aborbed by skin/skin burn/skin tan) eye lens is on resonance(waves absorbed by lens/don’t reach the retina(can’t see UV). Water is on resonance. We give off UV b/c we’re hot and environment is cold,
Term
 What is hard UV?
Definition
 Smaller wavelengths, causes skin burn, doesn't pass through glass
Term
 What is soft UV?
Definition
 Longer wavelengths, doesn't cause skin burn, passes through glass
Term
 What does visible light do?
Definition
 o   Visible light: the narrow range of wavelenths which are on resonance for the human retina. Different wavelengths are on resonance for different photo recpetors allowing us to see color. 400nm-700nm
Term
 What does Infra-red do?
Definition
 o   Infra-red: human skin is on resonance(waves absorbed by skin, energy rises, skin feels warm) human retina is off resonance(waves pass thru with no interaction, we don’t see it) liquid is on resonance. Makes us feel warm. Insects can see it because they don’t have liquid eyes. Remotes use it, they use it for eye exams, detect radiation, see warm and cold currents, see if you are lying
Term
 What do microwaves do?
Definition
 o   Microwaves: shakes the water to heat it up, defrost means less amplitude, water is on resonance, absorbs energy, heats up. (more efficient than conventional ovens which heat air)
Term
Definition
 o   Radiowaves: radar (the time it takes it to come back tells the chip the speed of the car), soundwaves are sent out to detect objects under water-sonar, Whales use sonar to see, AM (amplitude modulated) FM (frequency modulated), can see through clouds up to 1m, radar used to detect storm front b/c they bounce off clouds with 100km wavelength so you can map where the clouds are
Term
 What happens when you raise the temperature?
Definition
 o   Raise temperature-charges wiggle faster-wave frequency increases. As you raise temp, glows red than orange, can determine temp from color. Increase temp-range of frequency increase-eventually white light.
Term
 What type of light passes through clouds?
Definition
 UV passes through clouds, visible light doesn't
Term
 What happens when radiation passes through the atmosphere?
Definition
 Much of the IF is absorbed in the water of the atmosphere
Term
 What happens to the UV in the atmosphere?
Definition
 It is absorbed
Term
 How thick is the ozone?
Definition
 1/8th of an inch
Term
 What is the greenhouse effect?
Definition
 Light passes in and is absorbed by the plant, the plant gives off infrared, the infrared wont pass through the glass and that creates the heat. UV can't pass thru glass either
Term
 How is the greenhouse effect applied to global warming?
Definition
 The carbon dioxide acts like glass
Term
 How does light make color?
Definition
 It has to go through the atmosphere
Term
 What is incandescence?
Definition
 Heat up an object and gives off light ex.the sun, coal
Term
 What is an ARC-lamp?
Definition
 Electrons accelerated by voltage, smash into carbon plate, heating it up. Very bright, used in theaters
Term
 What is a light bulb?
Definition
 Incandescent. Electrical resistance causes filament to warm up, filament then radiates. Very inefficient because it peaks in the infra-red
Term
 What is a tungsten-halogen light?
Definition
 Higher temperature with a containing halogen which makes the filament take longer to evaporate
Term
 Which light is "good light" and why?
Definition
 florescent because it radiates more light, less heat, voltage causes electrons to accelerate hitting gas molecules, causing them to wiggle. The molecule wiggles at its resonant frequency gives off light at the resonant frequency
Term
 What type of color do these gasses give off? Neon? Mercury? Krypton?
Definition
 Neon= red-orange. Mercury=blue-green, Krypton= pale blue
Term
 What are high intensity discharge lamps?
Definition
 Mercury lamps. Last 1000 years. Pale blue tint that lasts really long, only light no heat, efficient but mercury is really toxic
Term
 What is a florescent tube?
Definition
 Not incandescent, the shaking creates light. Electrode voltage accelerates electrons. These collide with gas molecules which shake on resonance, giving off UV radiation, phosphorous coating converts UV to visible
Term
 Why don't people like florescent light?
Definition
 It is more harsh, it gives out radiation at specific times unlike tungsten which is steady like the sun
Term
 When do you use florescence?
Definition
 For tagging molecules, art authenticity, police finger printing, and find it in nature
Term
 Where do you find natural light that is not incandescent?
Definition
 Lightening is not incandescent it is more like the efficient tubes, doesn't require heat for light. The northern lights aren't incandescent either
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