Quiz 1 Flashcards
If you have a 100 watt light bulb how much energy does it use each minute
6,000 Jules
The frequency of a wave is
The number of peaks passing by an point each second
Measured in cycles per second
Measured in hertz
Equal to the speed of the wave divided by the length of the wave
How are wavelength, frequency, and energy related
Longer wavelength means lower frequency and lower energy
What is true about x rays and radio waves
X rays and radio waves are both forms of light or electromagnetic radiation
X rays have shorter wavelengths than radio waves
X rays have higher frequency than radio waves
X rays have higher energy than radio waves
An electron volt is…
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 electron falls back to lower energy levels the gas produces what?
An emission line spectrum
When an electron in an atom goes from a higher energy state to a lower energy state, the atom
Emits a photon of a specific frequency
White light pass through a cloud of gas. After passing through the gas, when we see this light we see what?
An absorption like spectrum
What is always true about thermal radiation?
A hot object emits photons with a higher average energy than a cool object
You observe the same spectral line in two stars that are identical in every way except that one rotated faster than the other. How does the spectral line differ between the two?
The kind in the faster rotating Star is broader
What is the difference between energy and power
Power is the rate at which energy is used, so it’s units are a unit of energy divided by a unit of time
Supposed you know the frequency of a photon and the speed of light. What else can you determine about the photon?
It’s wavelength and energy
When considering light as made up of individual pieces each characterized by a particular skinny of energy, the pieces are called what?
Photons
From shortest to longest wavelength what is the correct order of the electromagnetic radiation categories
GUVIR
Gamma rays, X rays, ultraviolet, visible light, infrared, radio
Thermal radiation is defined as
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
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?
The wavelengths if spectral lines in the stars spectrum
The spectra of most galaxies show redshirts. This means that their spectral lines are what?
Have wavelengths tat are longer than normal
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers. A partial stars spectrum shows the same hydrogen line at a wavelength of 486. What can we conclude?
The Star is moving towards 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?
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?
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?
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 (think about the laws of radiation)
The blue star has a hotter 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?
The line in the faster rotating star is broader
