Astronomy - First Exam Correctly Answered.
Light acts like? - CORRECT ANSWER both a wave and particle
Rank the following in order of decreasing wavelength?
gamma rays, visible light, infrared light, ultraviolet light, radio waves - CORRECT ANSWER radio waves, infrared, visible light, ultra...
Why is an iron atom a different element from a sodium atom? - CORRECT ANSWER An iron atom has
more protons in its nucleus than a sodium atom has. A given element is defined by its number of
protons.
Suppose an atom has three energy levels, specified in arbitrary units as 10, 7, and 5. In these units,
which of the following energies might an emitted photon have? - CORRECT ANSWER 3, 2, 5 since we
have 10-7, 10-5, and 7-5
When a boat moves through the water, the waves in front of the boat bunch up, while the waves behind
the boat spread out. What is this an example of? - CORRECT ANSWER the Doppler effect. The Doppler
effect explains why waves are compressed in the direction of motion and stretched out in the opposite
direction
As a blackbody becomes hotter, it also becomes ___ and ___. - CORRECT ANSWER More luminous and
bluer
Two stars are of equal luminosity. Star A is 3 times as far from you as star B. Star A appears ___ star B. -
CORRECT ANSWER 1/9 as bright. Star A is father so it must appear fainter. Since brightness scales as
1/d^2 it will appear 3^2=9 times fainter
When less energy is radiated from a terrestrial planet, its ___ increased until new ___ - CORRECT
ANSWER temperature; equilibrium. If less energy is radiated away, the energy is trapped, making the
temperature increase to a new equilibrium level
, Is the frequency of a photon related to the energy of a photon? - CORRECT ANSWER True. E=hf
Does blue light have more energy than red light? - CORRECT ANSWER True. Blue light has more energy
than red light.
Can an atom emit or absorb a photon of any wavelength? - CORRECT ANSWER False. An atom can only
emit energies corresponding to the quantized energy levels of its electrons
Is the emission spectrum of a helium atom identical to that of a carbon atom? - CORRECT ANSWER False.
Every atom has its own energy levels, depending on the size and charge of the nucleus and the electron
structure
Do cooler objects radiate more of their total light at shorter wavelengths than do hotter objects? -
CORRECT ANSWER False. Cooler objects radiate redder light.
Suppose you have two monochromatic light beams. Beam 1 has half the wavelength of beam 2. How do
their frequencies compare? - CORRECT ANSWER Beam 1 has 2 times the frequency of beam 2.
Frequency and wavelength are inversely related, so if the wavelength is half, the frequency is double
How does the speed of light in a medium compare to the speed of the vacuum? - CORRECT ANSWER The
speed in the medium is always slower than the speed in the vacuum. In any medium, light slows down.
Momentum is the product of what? - CORRECT ANSWER mass and energy. This is the classical definition
When an electron moves from a higher energy level in an atom to a lower energy level, a photon does
what? - CORRECT ANSWER a photon is emitted. A downward transition gives off energy, meaning a
photon is emitted.
Star A and star B appear equally bright in the sky. Star A is twice as far away from Earth as star B. How
do the luminosities compare? - CORRECT ANSWER Star A is 4 times as luminous as star B. Brightness
sacles as L/d^2 so if star A is twice as far away, it must have 2^2=4 times more luminosity to appear as
bright as star B.
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