ASTR 1210 Homework 9
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Interaction with light? Visible light meets clear glass Cell phone signals pass through walls
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Transmission
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Interaction with light? Visible light does not pass through a black wall Blue light hits a red sweatshirt
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Absorption
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Interaction with light? Red light hits a red sweatshirt White light hits a white piece of paper
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Reflection or Scattering
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Interaction with light? Light comes from your computer screen Light comes from a light bulb
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Emission
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If a material is highly opaque, then it _____
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absorbs most light
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Grass (that is healthy) looks green because _______
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it reflects green light and absorbs other colors
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Everything looks red through a red filter because _______
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the filter transmits red light and absorbs other colors
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the frequency of a wave is
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All of the following: measured in cycles per second the number of peaks passing by any point each second equal to the speed of the wave divided by the wavelength of the wave measured in hertz (Hz)
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The wavelength of a wave is
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the distance between two adjacent peaks of the wave
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How are wavelength, frequency and energy related for photons of light?
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Longer wavelength means lower frequency and lower energy
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From lowest energy to highest energy, rank the different categories of electromagnetic radiation
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radio, infrared, visible light, ultraviolet, X rays, gamma rays
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Which of the following statements about X rays and radio waves is not true? X rays and radio waves are both forms of light, or electromagnetic radiation. X rays have higher frequency than radio waves. X rays travel through space faster than radio waves. X rays have higher energy than radio waves. X rays have shorter wavelengths than radio waves.
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X rays travel through space faster than radio waves
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We can see each other in the classroom right now because we _____
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reflect visible light
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All wavelengths of visible light reach Earth's surface, which is why we can see all colors and why visible-light telescopes work fine on the ground
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Rank the following from highest altitude absorbed to lowest (earth's surface Infrared light X rays most radio waves most ultraviolet light green visible light
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Highest to Lowest 1. X rays 2. most ultraviolet light 3. most infrared light 4. most radio waves and green visible light radio and visible light telescopes work on the surface infrared telescopes are useful on high mountain tops or airplanes UV telescopes can be lofted up with high altitude balloons X ray telescopes are only useful in space
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Reflecting or Refracting telescopes? world's largest telescope incoming light passes through glass the world's largest is 1-meter in diameter most commonly used by professional astronomers today very large telescopes become \"top-heavy\" The Hubble telescope Galileo's telescope
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Reflecting Telescopes: world's largest telescope most commonly used by professional astronomers today The Hubble Space Telescope Refracting Telescopes: incoming light passes through glass The world's largest is 1-meter in diameter Very large telescopes become \"top-heavy\" Galileo's telescopes
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Larger mirrors have a larger light collecting area. Remember that the light collecting area is proportional to the square of the mirror diameter
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Which forms of light can be observed with telescopes at sea level?
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Visible light and Radio Waves
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If our eyes were sensitive only to X rays, the world would appear _______
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dark because X-ray light does not reach Earth's surface
