if you have a 100-watt light bulb, how much energy does it use each minute?
the frequency of a wave is?
measured in hertz, the number of peaks passing by a point each second, measured in cycle per second and equal to the speed of the wave divided by the wavelength.
how are wavelength, frequency and energy related to photons of light?
longer wavelength means, lower frequency and lower energy
which of the following statements about xrays and radio waves is not true?
xrays travel through space faster 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 bumpign electrons to higher energy levels whne the electrons falls back to lower energy levels the gas produces?
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 specific frequency.
when white ligth passes through a cool cloud of glass we see?
an absoprtion line spectrum
which of the following statements about thermal radiation is always true?
a hot object emits more total radiation per unit surface area 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?
the line 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 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?
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?
from shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation.
gamma ray, x-ray, ultraviolet visible light, infrared, radio
thermal radiation is defined as
radiation with a spectrum that depends only on the emitting object's temperature
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 info is the most useful to you?
the wavelengths of spectral lines in the star's spectrum
the spectra of most galaxies show redshifts, this means their spectral lines are
have wavelengths that are longer than normal
laboratories show hydrogen produces a spectral line at a wavelength of 486.1 nanometers. A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
the star is moving toward us
in what part of the spectrum would you need to be able to see so that you coudl be able to detect the light emitted by students in an astronomy class
which two are the basic premises for the special theory of relativity
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
observers in different reference frames may disagree about the basic laws of nature.
in relativity, two people share the same frame of reference only if
they are not moving relative to each other
bob is coming toward you at a speed at 75km/hr, you throw a baseball at Bob at 75km/hr, what does he see the ball doing?
he sees the ball coming at him at 150km/hr
if you see jackie going to your left at exactly .99c and bob going to your right at exactly .99c, jackie will say that bob is
going away from her faster than .99c, but slower than c
a spaceship is headed toward alpha centauri at .999c, according to us, the distance of alpha centauri is about 4 light-years. how far is alpha centauri according to the travelers in the ship?
quite a bit less than 4 light-years
a spaceship is moving past us at close to the speed of light: how would we view time as it goes by one the ship?
their clocks are moving slower than ours.
a spaceship is moving past us at close to the speed of light:if we could measure the mass of a ship as it passes by what would it be?
its mass is greater than its rest mass
a spaceship is moving past us at close to the speed of light:how would the passengers on the spaceship view our clocks
our clocks are going slow
how does the explosion of the nuclear bomb provide evidence of the theory of relativity?
the bomb produces energy in accord with E = mc^2, which is part of the theory of relativity.
A man is moving past you at close to the speed of light, which of the following accurately describes the effects on mass, size and time?
his mass would be increased from its value at rest, his lenght would be decreased by his value at rest but only from the direction in which he is moving, and his time would be running slower than yours.
why do the predicted consequences of the special theory of relativity seem so strange to us?
because they are obviously only at speeds that we never experience in our daily lives
in the late 1800s helmholtz and kelvin suggested that the sun stayed hot due to gravitational contraction. What was the major drawback of this theory?
it predicted the sun could only last 25 million years, which is far less than the age of the Earth
what do we mean when we say the sun is in gravitational equilibrium?
there is a balance within the sun between the outward push of pressure and inward pull of gravity
What is the sun made of?
70 percent hydrogen, 28 helium, and 2 percent other elements
what are the appropriate units for the sun's luminosity
what is the average surface temp of the sun
what is the temperature of the sun's core
10 million K
from the center outward, which of the following lists the sun's layers in the correct order?
why do sunspots appear darker in pictures of the sun?
they are actually fairly bright they just appear darker vs the even brighter surface of the surrounding sun
how does the sun generate energy today?
at the center of the sun, fusion converts hydrogen into
helium, energy and neutrinos
suppose you put two protons near each other because of their electromagnetic forces they will
repel each other
the first step in proton-proton chain produces an antielectron or positron, what happens to the positron?
it is rapidly converted to energy when it meets an ordinary electron, resulting in matter-antimatter annihilation
the overall fusion reaction buy which the sun creates energy is
4H=->1He + energy
which statement best describes the solar neutrino problem?
solar neutrinos have been detected , but in fewer numbers than predicted by theoretical models
why are neutrinos so hard to detect
because they rarely have contact with matter
what is a possible solution to the neutrino problem
the neutrinos created in the sun change into different neutrinos that we can't detect
what happens to energy the sun creates in the convection zone
energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.
most of the energy produced in the sun is released in the form of visible light from the photosphere. however some energy is released from upper layers of the solar atomsphere. what best describes where the other forms of light are released
the chromosphere is a source of UV light and the corona is the source of xrays
what is granulation in the sun?
the bubbling pattern on the photosphere produced by underlying convection
what processes are involved in the sunspot cycle
the winding of magnetic fields lines due to differential rotation
what observations characterize solar maximum
we see many sunspots on the surface
since stars begin their lives with the same basic composition what characteristics decide how they will differe
mass they are formed with
what are the standard units for luminosity
a star's luminosity is
total amount of light a star radiates at each second
what are the standard units for apparent brightness
watts per square meter
if the distance between us and the star is doubled, with everything else remaining the same, the luminosity...
remains the same, but the apparent brightness is decreased by a factor of four
why do astronomers measure the visible-light apparent brightness instead of the total apparent brightness of a star
longest answer...measuring brightness in all wavelengths is too hard to do.
suppose you measure the parallax angle of a star to be 0.1 arcsecond...the distance to the star is
10 parsecs away
the most distant stars we can measure stellar parallax for are approximately
100 parsecs away
the spectral sequence sorts stars according to
the spectral sequence in order of decreasing temp is
why is the spectral sequence of stars not in alphabetical order
the original alphabetical order didn't correspond to temp so it had to be redone
which statement about spectral star types is true
all are true
2 stars, same spectral line type
star 1 is 10 times
which term is given to a pair of stars that appear to change positions in the sky indicating they orbit each other
which term is given to a pair of stars that indicate they orbit each other only via their periodic Doppler shifts
on the Hertzprung-Russel diagram where would we find stars that are cool and dim
on the Hertzprung-Russel diagram where would we find stars that are cool and luminous
on the Hertzprung-Russel diagram where would we find stars that have the largest radii
on the Hertzprung-Russel diagram where would we find white dwarfs
on the Hertzprung-Russel diagram where would we find red giants
you observe a star in the disk of the milky way you want to plot the star on the H-R diagram you will need to determine everything except
rotation rate of the star
on the main sequence stars obtain their energy
by converting hydrogen to helium
a star of spectral type G lives approximately how long on the main sequence
10 billion years
whihc is true about low-mass stars as compared to high-mass stars
low mass stars are cooler and less luminous than high mass stars
which of the following luminosity classes refers to stars that are categorized on the main sequence
an open cluster is...
alll stars in the cluster are approximately the same age