Astronomy Exam 2
Which object emits more infrared radiation?
A star that is the same size as the Sun but five times hotter
This diagram shows the approximate depths to which different wavelengths of light penetrate Earth's atmosphere. If we had no atmosphere.
All of these are true.
Which kind of telescope did Newton invent that allowed for telescopes to be shorter?
a reflecting telescope
The absorption line spectrum shows what we see when we look at a hot light source (such as a star or light bulb) directly behind a cooler cloud of gas. Suppose instead that we are looking at the gas cloud but the light source is off to the side instead of directly behind it. In that case, the spectrum would __________.
be an emission line spectrum
If you have a telescope that is observing light with wavelengths of a few meters, you are observing __________.
radio waves
X ray photons have a _____ wavelength, _____ frequency, and _____ energy than do ultraviolet photons.
shorter, higher, higher
Compared to a cold object, a hotter object of the same size emits most of its light at __________ wavelengths and emits _____ light overall.
shorter, more
Notice that the Sun's spectrum appears brightest (or most intense) in the yellow-green region. This fact tells us __________.
the approximate temperature of the Sun's surface
Any spectrum can be displayed either in photographic form as shown to the left or as a graph. Which of the following graphs could represent a portion of the Sun's visible light spectrum?
the graph where red lines are pointing down
Which telescope has a better (smaller) angular resolution: a 2-m telescope observing visible light (wavelength 5.0×10-7 m) or a 10-m radio telescope observing radio waves (wavelength 2.1×10-2 m)?
the optical telescope
When you listen to the radio, you are hearing
(sound waves) if not an answer choice then none of the above
How much greater is the light-collecting area of a 4-m telescope than that of a 1-m telescope?
16 times greater
Suppose you find a rock and measure that 12.5% of the original uranium-235 still remains it, while the other 87.5% has decayed into lead-207. About how old is the rock?
2.1 billion years
Consider the total amount of light collected by a 4-m telescope observing a star for 10 minutes. If you wanted to collect the same amount of light with a 2-m telescope, how long would you have to observe?
40 minutes
If an atom contained only four energy levels (such as in the figure below), how many possible different emission lines could it emit? Hint: Be sure to count all the possible transitions that give emission lines.
6
Suppose we want to know what the Sun is made of. What should we do?
Compare the wavelengths of lines in the Sun's spectrum to the wavelengths of lines produced by chemical elements in the laboratory.
Infrared Telescope
Determine the surface temperature of Venus. Study a dense cloud of cold gas in space.
Time Monitoring
Does the star Mira vary in brightness? Is the X-ray emission from the galactic center steady or changing?
Comte was proven wrong in his claim that we could never learn the composition of stars. What do we know today that Comte did not know when making his claim, and that makes it possible for us to learn the chemical compositions of stars?
Every chemical element produces a unique spectral fingerprint.
Refracting Telescopes
Galileo's Telescope incoming light passes through glass very large telescopes become "top heavy" The world's largest 1- meter in diameter
Imaging
How large is the Andromeda Galaxy Are stars in the Orion Nebula surrounded disks of gas What are the major surface features of Mars
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?
Incandescent bulbs emit most of their energy as infrared light
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?
Incandescent bulbs emit most of their energy as infrared light.
Spectroscopy
Is the star Vega moving toward us or away from us? What is the chemical composition of the Crab Nebula? What is the temperature of Jupiter's atmosphere?
Which of the following statements about the double slit experiment is false?
It produces the same results for marbles and bowling balls as it does for electrons and photons.
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?
It would be very similar to the spectrum of the human.
What is the Oort cloud?
It's not really a cloud at all, but rather refers to the trillion or so comets thought to orbit the Sun at great distances.
What are four key features of our solar system that any theory of solar system formation must be able to explain?
Large bodies have orderly motions. Planets fall into two major categories. There are vast numbers of asteroids and comets. There are a few notable "exceptions to the rules."
Emission
Light comes from your computer screen Light comes from a light bulb
This diagram shows the approximate depths to which different wavelengths of light penetrate Earth's atmosphere. Why does it show an airplane?
Much of the infrared spectrum can be observed from an airplane that flies above most clouds
Xray Telescope
Observe the hot (1-million K) gas in the Sun's corona. Look for high-energy radiation from a supernova.
Visible Telescope Telescope
Obtain a spectrum of the sunlight reflected by Mars. Measure the brightness of a star that is similar to our Sun.
Which of the following procedures would allow you to make a spectrum of the Sun similar to the one shown, though with less detail?
Pass a narrow beam of sunlight through a prism.
Suppose you go outside and look at three stars. Star A is blue, Star B is white, and Star C is red. Which star is the hottest and which star is the coldest?
Star A is the hottest and Star C is the coldest.
Assuming that other planetary systems form in the same way as our solar system formed, where would you expect to find terrestrial planets?
Terrestrial planets will likely be located nearer the planetary system's star than any jovian planets.
Which of the following best describes why the Sun's spectrum contains black lines over an underlying rainbow?
The Sun's hot interior produces a continuous rainbow of color, but cooler gas at the surface absorbs light at particular wavelengths.
The "extraordinary" part of Comte's claim was his statement that we could never learn the composition of stars. Which of the following best summarizes the key lesson we should learn from the fact that his claim was ultimately proven wrong?
The advance of science and technology may someday provide ways to answer questions that seem unanswerable today.
Which of the following types of light cannot be studied with telescopes on the ground?
X-Rays
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?
The planet emits virtually all its light as infrared light. The star's spectrum peaks in visible light. The star emits much more total light than the planet.
The first telescopic photo shows what appears to be a single star. The second photo shows the same object, now revealed to be two distinct stars. What is the difference between the two photos?
The second photo has better (smaller) angular resolution than the first photo.
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?
The star emits much more total light than the planet. The planet emits virtually all its light as infrared light. The star's spectrum peaks in visible light.
Which of the following statements is not a valid advantage for having a telescope in orbit above our atmosphere?
The telescope is closer to the astronomical objects.
Study the graph of the intensity of light versus wavelength for continuous spectra, observing how it changes with the temperature of the light bulb. Recall that one of the laws of thermal radiation states that a higher-temperature object emits photons with higher average energy (Wien's law). This law is illustrated by the fact that for a higher temperature object, the graph peaks at __________.
a shorter wavelength
The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is:
above Earth's atmosphere.
What type of visible light spectrum does the Sun produce?
an absorption line spectrum
Which of the following type of spectrum would you expect if you view star light that has passed through a cool cloud of interstellar gas on its way to Earth?
an absorption line spectrum
Can learn from a single spectrum
chemical composition (surface) surface temperature speed toward or away from us
If our eyes were sensitive only to X rays, the world would appear __________.
dark because X-ray light does not reach Earth's surface
We divide the electromagnetic spectrum into six major categories of light, listed below. Rank these forms of light from left to right in order of increasing wavelength. To rank items as equivalent, overlap them.
gamma rays, xrays, ultraviolet, visible light, infrared, and radio waves
If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?
in space
Which of the following are forms of light (electromagnetic radiation)?
infrared visible light X rays ultraviolet microwaves gamma rays radio waves
The James Webb Space Telescope is designed primarily to observe __________
infrared light
Cannot learn from a single spectrum
interior temperature speed across our line sight size (diameter) mass distance
Thermal radiation gets its name because __________.
its spectrum depends on the temperature of the object emitting it
Red light has a _____ wavelength and a _____ frequency than does blue light.
longer, lower
In the illustration of the solar spectrum, the upper left portion of the spectrum shows the __________ visible light.
lowest frequency
We expect a scientific theory to be able to make predictions that can be tested. Which of the following is a prediction of the nebular theory that has been verified by observations?
many stars should have planets
Compared to terrestrial planets, jovian planets are __________.
more massive and lower in average density
The twinkling of stars is caused by:
motion of air in our atmosphere
Click "show" for the emission line spectrum, then click "choose gases" and study the emission line spectrum for neon. The neon "OPEN" sign appears reddish-orange because __________.
neon atoms emit many more yellow and red photons than blue and violet photons
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?
nothing
Rank the forms of light from left to right in order of increasing speed. To rank items as equivalent, overlap them. (TOP TO BOTTOM CENTER)
radio waves infrared visible light ultraviolet xrays gamma rays
Which of the following forms of light can be observed with telescopes at sea level?
radio waves and visible light
Rank the forms of light from left to right in order of increasing energy. To rank items as equivalent, overlap them.
radio waves, infrared, visible light, ultraviolet, xrays, gamma rays
Rank the forms of light from left to right in order of increasing frequency. To rank items as equivalent, overlap them.
radio waves, infrared, visible light, ultraviolet, xrays, gamma rays
Reflecting or Scattering
red light hits a red sweatshirt white light hits a white piece of paper
Which kind of telescope did Newton invent that allowed for telescopes to be shorter?
reflecting telescope
Which of the following forms of light can be observed with telescopes at sea level?
visible light and radio waves
Absorption
visible light does not pass through a black wall blue light hits red sweatshirt
Transmission
visible light meets clear glass. cell phone signal passes through wall
Suppose you know the frequency and speed of light. What else can you determine?
wavelength and energy (both)
Reflecting Telescopes
worlds largest, mostly used by astronomers today and the hubble space telescope
If the angular separation of two stars is larger than the angular resolution of your eyes,
you will be able to see both stars
