PHYS 187 Exam 1 Questions with Verified Solutions Graded A+
If you have a 100-watt light bulb, how much energy does it use each minute? - Answers 6,000
joules
The frequency of a wave is - Answers The number of peaks passing by any point each second,
measured in cycles per second, measured in hertz (Hz), equal to the speed of the wave divided
by the wavelength of the wave, AKA all of the above
How are wavelength, frequency and energy related for photons of light? - Answers Longer
wavelength means lower frequency and lower energy
Which of the following statements about x rays and radio waves is not true? - Answers X rays
travel through space faster than radio waves
An electron-volt is - Answers an amount of energy much smaller than a joule
If you heat a gas so that collisions are continually bumping electrons to higher energy levels,
when the electrons fall back to lower the energy levels the gas produces - Answers an emission
line spectrum
When an electron in an atom goes from a higher energy state to lower energy state, the atom -
Answers emits a photon of a specific frequency
When white light passes through a cool cloud of mass, we see - Answers an absorption line
spectrum
Which of the following statements about thermal radiation is always true? - Answers A hot
object emits more total radiation per unit surface than a cool object
You observe the same spectral line in two stars that are identical in every way except that one
rotates faster than the other. How does the spectral line differ between the two? - Answers the
line in the faster rotating star is broader
What is the difference between energy and power? - Answers Power is the rate at which energy
is used, so its units are a unit of energy divided by a unit of time
Suppose you know the frequency of a photon and the speed of light. What else can you
determine about the photon? - Answers its wavelength and energy
When considering light as made up of individual "pieces," each characterized by a particular
amount of energy, the pieces are called - Answers photons
From shortest to longest wavelength, which of the following correctly orders the different
categories of electromagnetic radiation? - Answers gamma rays, x rays, ultraviolet, visible light,
infrared, radio
, Thermal radiation is defined as - Answers radiation with a spectrum whose shape depends only
on the temperature of the emitting object
According to the laws of thermal radiation, hotter objects emit photons with - Answers a shorter
average wavelength
Suppose you want to know the chemical composition of a distant star. Which piece of
information is most useful to you? - Answers The wavelength of spectral lines in the star's
spectrum
The spectra of most galaxies show redshifts. This means their spectral lines - Answers have
wavelengths that are longer than normal
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1
nanometers (nm). A particular stat's spectrum show the same hydrogen line at a wavelength of
486.0 nm. What can we conclude? - Answers the star is moving toward us
In what part of the spectrum would you need to be able to see so that you could detect the light
emitted by students in astronomy class? - Answers Infrared
You observe a distant galaxy. You find that a spectral line normally found in the visible part of
the spectrum is shifted toward the infrared. What do you conclude? - Answers The galaxy is
moving away from you
If one object has a large redshift and another object has a small redshift, what can we conclude
about these two objects? - Answers The one with the large redshift is moving away from us
faster than the one with the small redshift
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). - Answers The blue star has a hater surface temperature than the red star.
You observe the same spectral line in two stars that are identical in every way except that one
rotates faster than the other. How does the spectral line differ between the two? - Answers The
line in the fast rotating star is broader
If two objects are the same size but one object is 3 times hotter than the other object, the hotter
object emits - Answers 81 times more energy
Each of the following lists two statements. Which two are the basic premises for the special
theory of relativity? - Answers 1. The laws of nature are the same for everyone. 2. The speed of
light is the same for everyone.
Which of the following is not a prediction made by the theory of relativity? - Answers Observers
in different reference frames may disagree about the basic laws of nature.
If you have a 100-watt light bulb, how much energy does it use each minute? - Answers 6,000
joules
The frequency of a wave is - Answers The number of peaks passing by any point each second,
measured in cycles per second, measured in hertz (Hz), equal to the speed of the wave divided
by the wavelength of the wave, AKA all of the above
How are wavelength, frequency and energy related for photons of light? - Answers Longer
wavelength means lower frequency and lower energy
Which of the following statements about x rays and radio waves is not true? - Answers X rays
travel through space faster than radio waves
An electron-volt is - Answers an amount of energy much smaller than a joule
If you heat a gas so that collisions are continually bumping electrons to higher energy levels,
when the electrons fall back to lower the energy levels the gas produces - Answers an emission
line spectrum
When an electron in an atom goes from a higher energy state to lower energy state, the atom -
Answers emits a photon of a specific frequency
When white light passes through a cool cloud of mass, we see - Answers an absorption line
spectrum
Which of the following statements about thermal radiation is always true? - Answers A hot
object emits more total radiation per unit surface than a cool object
You observe the same spectral line in two stars that are identical in every way except that one
rotates faster than the other. How does the spectral line differ between the two? - Answers the
line in the faster rotating star is broader
What is the difference between energy and power? - Answers Power is the rate at which energy
is used, so its units are a unit of energy divided by a unit of time
Suppose you know the frequency of a photon and the speed of light. What else can you
determine about the photon? - Answers its wavelength and energy
When considering light as made up of individual "pieces," each characterized by a particular
amount of energy, the pieces are called - Answers photons
From shortest to longest wavelength, which of the following correctly orders the different
categories of electromagnetic radiation? - Answers gamma rays, x rays, ultraviolet, visible light,
infrared, radio
, Thermal radiation is defined as - Answers radiation with a spectrum whose shape depends only
on the temperature of the emitting object
According to the laws of thermal radiation, hotter objects emit photons with - Answers a shorter
average wavelength
Suppose you want to know the chemical composition of a distant star. Which piece of
information is most useful to you? - Answers The wavelength of spectral lines in the star's
spectrum
The spectra of most galaxies show redshifts. This means their spectral lines - Answers have
wavelengths that are longer than normal
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1
nanometers (nm). A particular stat's spectrum show the same hydrogen line at a wavelength of
486.0 nm. What can we conclude? - Answers the star is moving toward us
In what part of the spectrum would you need to be able to see so that you could detect the light
emitted by students in astronomy class? - Answers Infrared
You observe a distant galaxy. You find that a spectral line normally found in the visible part of
the spectrum is shifted toward the infrared. What do you conclude? - Answers The galaxy is
moving away from you
If one object has a large redshift and another object has a small redshift, what can we conclude
about these two objects? - Answers The one with the large redshift is moving away from us
faster than the one with the small redshift
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). - Answers The blue star has a hater surface temperature than the red star.
You observe the same spectral line in two stars that are identical in every way except that one
rotates faster than the other. How does the spectral line differ between the two? - Answers The
line in the fast rotating star is broader
If two objects are the same size but one object is 3 times hotter than the other object, the hotter
object emits - Answers 81 times more energy
Each of the following lists two statements. Which two are the basic premises for the special
theory of relativity? - Answers 1. The laws of nature are the same for everyone. 2. The speed of
light is the same for everyone.
Which of the following is not a prediction made by the theory of relativity? - Answers Observers
in different reference frames may disagree about the basic laws of nature.
