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ASTRO-1 CH.5 HW
Terms in this set (40)
The diagrams below each show the motion of a distant star relative to Earth (not to scale). The red arrows indicate the speed and direction of the star's motion: Longer arrows mean faster speed. Rank the stars based on the Doppler shift that we would detect on Earth, from largest blueshift, through no shift, to largest redshift.
Each diagram below shows a pair of spectra with a set of spectral lines. The top spectrum always shows the lines as they appear in a spectrum created in a laboratory on Earth ("Lab") and the bottom spectrum shows the same set of lines from a distant star. The left (blue/violet) end of each spectrum corresponds to shorter wavelengths and the right (red) end to longer wavelengths. Rank the five stars based on the Doppler shifts of their spectra, from largest blueshift, through no shift, to largest redshift.
An important line of hydrogen occurs at a rest wavelength (as measured in a laboratory) of 656 nm (a nanometer (nm) is a billionth of a meter). Each diagram below has this line labeled with its wavelength in the spectrum of a distant star. Rank the motion of the stars along our line of sight (radial motion) based on their speed and direction, from moving fastest toward Earth, through zero (not moving toward or away from Earth), to moving fastest away from Earth.
The _____ allows us to determine how fast Mars is moving toward or away from us.
We determine Mars's surface temperature from the peak wavelength of the_____ it emits.
The color of Mars in our sky is determined by the ______ of Mars's spectrum.
Carbon dioxide in Mars's atmosphere produces ______ in the infrared portion of its spectrum.
Hot gas in Mars's upper atmosphere produces _____ in the ultraviolet portion of its spectrum.
Why does Mars appear reddish in color?
It reflects most of the Sun's red light while absorbing most of its blue light.
Suppose that Mars had a higher surface temperature. How would its spectrum be different?
The peak in the infrared would be at shorter wavelength.
Which of the following statements is true of green grass?
It absorbs red light and reflects green light.
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?
They have a frequency of 2 hertz.
Which statement about photons of light is true?
An infrared photon has less energy than an X-ray photon, but travels at the same speed.
How are wavelength, frequency, and energy related for photons of light?
Longer wavelength means lower frequency and lower energy.
Which object is likely to be the coldest? The object whose light spectrum is brightest in the
Compared to red light, blue light has higher frequency and
Higher energy and shorter wavelength
Radio waves are
A form of light.
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.
Rank the forms of light from left to right in order of increasing frequency. To rank items as equivalent, overlap them.
Rank the forms of light from left to right in order of increasing energy. To rank items as equivalent, overlap them.
Rank the forms of light from left to right in order of increasing speed. To rank items as equivalent, overlap them.
Listed following are various physical situations that describe how light interacts with matter. Match these to the appropriate category.
Doppler shifted hydrogen absorption lines are seen in the spectrum of a star. The hydrogen line at 656.28 nm is seen to be shifted to 656.08 nm. Is the star moving towards or away from us, or can we not tell?
Moving towards us
Which of the following describes the light that can be detected from a person?
The person reflects many wavelengths of visible light and emits a continuum of wavelengths of infrared light.
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.)
The blue star has a hotter surface temperature than the red star.
If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
The planet is rotating.
From laboratory measurements, we know that a particular spectral line is formed by the rotation of the carbon monoxide molecule (CO) and it appears at a wavelength of 2.6007 millimeters (mm). The spectrum of an interstellar cloud of gas shows the same CO line appearing at a wavelength of 2.6008 mm. What can we conclude about the gas cloud?
The cloud is moving away from us.
The spectrum of Star A has an absorption line of hydrogen at 660.0 nm. The spectrum of Star B has an absorption line at 666 nm. The wavelength of this transition in the laboratory is 656.2 nm. What can I say about Star A and B?
Both stars are moving away from me, Star B is faster than Star A.
When an electron in an atom goes from a lower energy state to a higher energy state, the atom can
Absorb a photon of a specific frequency.
Which is hotter?
A blue star
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
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
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
What type of visible light spectrum does the Sun produce?
An absorption line spectrum
Lines of a particular element appear at the same wavelength in both emission and absorption line spectra.
The energy levels for electrons vary from one element to another.
A spectral line that appears at a wavelength of 321 nm in the laboratory appears at a wavelength of 328 nm in the spectrum of a distant object. We say that the object's spectrum is:
The simplified spectra for four stars is shown here. Which star has the lowest temperature?
Star D (purple line)
We know how fast a star in the galaxy is moving away from us on the basis of its
We know the Sun is primarily made from hydrogen and helium on the basis of its
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