AST 135

25 July 2022
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43 test answers

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question
Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?
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They have a frequency of 2 hertz
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transmission
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visible light meets clear glass cell phone signals pass through walls
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absorption
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visible light does not pass through a black all blue light hits a red sweatshirt
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reflection or scattering
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red light hits a red sweatshirt white light hits a white piece of paper
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emission
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light comes from a lightbulb light comes from your computer screen
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Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?
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The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.
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Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us __________.
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the approximate temperature of the Sun's surface
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Suppose we want to know what the Sun is made of. What should we do?
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Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory.
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forms of light (electromagnetic radiation)
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gamma rays microwaves ultraviolet infrared visible light x rays radio waves
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red light has a ___ wavelength and a ____ frequency than does blue light
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longer, lower
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xray photons have a ____ wavelength, _____ frequency, and _____ energy than do ultraviolet photons
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shorter, higher, higher
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If you have a telescope that is observing light with wavelengths of a few meters, you are observing __________.
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radio waves
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Suppose that you had "X-ray vision" that allowed you to see X rays. What would you notice when you looked at a friend standing near you that you could not notice with your visible light vision alone?
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nothing
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Thermal radiation gets its name because __________.
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its spectrum depends on the temperature of the object emitting it
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Compared to a cold object, a hotter object of the same size emits most of its light at __________ wavelengths and emits _____ light overall
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shorter, more
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Imagine being on the Moon and looking at the thermal radiation spectrum of Earth. How would it compare to the spectra shown on the graph in the video?
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It would be very similar to the spectrum of the human.
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Consider a planet orbiting another star that is very similar to our Sun. Assume the planet is about the size of Earth and has an Earth-like orbit around its star. Which of the following statements are true about the light coming from the star and planet?
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the planet emits virtually all its light as infrared light the star's spectrum peaks in visible light the star emits much more light than the planet
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Incandescent light bulbs emit thermal radiation because their filaments are heated to about 2500 Kelvin. LED light bulbs emit only at particular visible wavelengths. Why do incandescent bulbs require more energy to shine with the same amount of visible light as LED bulbs?
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Incandescent bulbs emit most of their energy as infrared light.
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shortest to longest wavelength
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gamma rays, x rays, ultraviolet, visible light, infrared, radio waves
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lowest to highest frequency
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radio waves, infrared, visible light, ultraviolet, xrays, gamma rays
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lowest to highest energy
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radio waves, infrared, visible light, ultraviolet, xrays, gamma waves
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speed
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all the same
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why is a sunflower yellow?
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it reflects yellow light
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blue light has higher frequency than red light. thus, blue light has
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higher energy and shorter wavelength than red light
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radio waves are
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a form of light
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compared to an atom as a whole, an atomic nucleus
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is very tiny but has most of the mass
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if you heat a rock until it glows, its spectrum will be
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a thermal radiation spectrum
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compared to the sun, a star whose spectrum peaks in the infrared is
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cooler
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What do we mean when we say that energy levels are quantized in atoms?
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We mean that the electrons can have only discrete values of electrical potential energy in atoms.
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Under what circumstances can energy level transitions occur?
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Electrons can make a transition from one level to another by taking in or emitting a specific amount of energy. If too much or too little energy is offered, the electron cannot make the transition.
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If a material is highly opaque, then it
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absorbs most light
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If a material is transparent, then it
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transmits light well
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Grass appears 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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the number of peaks passing by any point each second measured in cycles per second measured in hertz equal to the speed of the wave divided by the wavelength of the wave
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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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We can see each other in the classroom right now because we
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reflect visible light
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If you heat a gas so that collisions are continually bumping electrons to higher energy levels, when the electrons fall back to lower energy levels the gas produces
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an emission line spectrum
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When an electron in an atom goes from a higher energy state to a lower energy state, the atom
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emits a photon of a specific frequency
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We can learn a lot about the properties of a star by studying its spectrum. All of the following statements are true except one. Which one?
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The total amount of light in the spectrum tells us the star's radius.
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From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?
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The star is moving toward us.
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If one object has a large redshift and another object has a small redshift, what can we conclude about these two objects?
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The one with the large redshift is moving away from us faster than the one with the small redshift.
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Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)
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The blue star has a hotter surface temperature than the red star.