PHY 108 - Study Questions Set 2
1.
Parallax of a nearby star is used to estimate its
A.
distance from Earth.
B.
apparent magnitude.
C.
physical size or diameter.
D.
surface temperature.
2.
Suppose that, at night, the brightness of a light bulb is measured from a certain distance and then the light bulb is moved to a distance twice as far away. How bright will the light appear compared to the earlier measurement?
A.
1/16 as bright
B.
1/2 as bright
C.
1/8 as bright
D.
1/4 as bright
3.
What does apparent magnitude tell us about a star?
A.
its size compared to the Sun
B.
the intrinsic brightness of a star (the total light actually emitted by the star )
C.
the brightness of a star as it appears in our sky
D.
the brightness the star would appear to have if it were exactly 10 pc from the Earth
4.
At what distance are stars assumed to be from the Earth when they are represented by their absolute (as opposed to their apparent) magnitude?
A.
10 ly
B.
10 parsecs
C.
10 AU
D.
1 ly
5.
What effect does interstellar dust have on the apparent color of a star seen through the dust?
A.
The dust makes the star look brighter than it really is, but leaves the color of the star unchanged.
B.
The dust makes the star look bluer than it really is.
C.
The dust makes the star look fainter than it really is, but leaves the color of the star unchanged.
D.
The dust makes the star look redder than it really is.
6.
The spectrum of an ordinary main sequence star is a
A.
continuum of colors crossed by dark absorption lines, caused by absorption of cooler atoms and molecules at the surface.
B.
smooth continuum of color, peaking at a specific wavelength whose position is dependent on the surface temperature.
C.
series of emission lines, mostly from hydrogen, the major constituent of stellar surfaces, that occasionally overlap to produce sections of continuous color.
D.
continuum of colors crossed by brighter lines caused by emission of hot atoms and molecules on the surface.
7.
Where on the Hertzsprung-Russell diagram do most local stars in our universe congregate?
A.
in the supergiant area, where the most massive stars spend a significant time
B.
in the giants area, where most stars spend the longest time of their lives
C.
in the white dwarf area, the "graveyard" of stars
D.
on the main sequence where stars are generating energy by fusion reactions
8.
Measurements indicate that a certain star has a very high intrinsic brightness (100,000 times as bright as our Sun) and yet is relatively cool (3500 K). How can this be?
A.
There must be an error in observation, since no star can have this form.
B.
The star must be quite small.
C.
The star must belong to the main sequence.
D.
The star must be very large.
9.
An important aspect of binary star systems, as distinct from single stars, is that they allow a
A.
verification of the Doppler shift.
B.
measurement of the overall shapes of stars.
C.
measurement of the universal gravitational constant.
D.
measurement of the masses of stars.
10.
What condition is necessary for us to see eclipses of stars in binary star systems?
A.
One of the stars must be much bigger than the other so that it can hide its smaller companion when the orbital plane is at a large angle to the line of sight.
B.
The stars must have very similar surface temperatures whatever the inclination of their orbital plane to the line of sight, for us to see a significant eclipse.
C.
The line of sight from Earth to the star system must be in or very close to the orbital plane of the stars.
D.
The line of sight from Earth to the star system must be very close to the perpendicular to the orbital plane of the stars.
11.
The Sun's source of energy at the present time is thought to be
A.
thermonuclear fusion (combining) of hydrogen atoms.
B.
thermonuclear fission (splitting) of heavy elements into hydrogen.
C.
chemical burning of hydrogen gas with oxygen.
D.
gravitational contraction.
12.
The nuclei of which chemical elements are converted to other nuclei to produce the requisite energy in the thermonuclear process that heats the Sun?
A.
Helium is split into hydrogen.
B.
The abundant iron is successively split into lighter elements in a chain reaction to produce helium and hydrogen.
C.
Hydrogen is converted to helium.
D.
Carbon, nitrogen, and oxygen are used as catalysts in a chain reaction to combine hydrogen to produce helium.
13.
The phrase "hydrostatic equilibrium" in the Sun refers to
A.
the balance of gas pressure outward and magnetic forces inward.
B.
the creation of one helium nucleus for the "destruction" of every four hydrogen nuclei.
C.
the balance of gas pressure inward and heat outward.
D.
the balance of gravity inward and gas pressure outward.
14.
The mechanism at work when energy is transmitted by convection is
A.
the successive exchange of radiant energy between atoms.
B.
the passage of radiation through a gas.
C.
the fusion of hydrogen nuclei into helium nuclei.
D.
the mass motion of hot gases.
15.
The neutrino is
A.
a tiny particle that interacts very weakly with matter, with extremely low or zero mass and no charge.
B.
another name for the neutron, a component of almost all atomic nuclei, with a mass close to the proton and no charge.
C.
another name for a photon of very high energy, i.e., short wavelength electromagnetic radiation, with great penetrating power.
D.
a massive but very elusive nuclear particle that carries most of the energy generated in the core of the Sun to the surface, but that then decays to release electromagnetic radiation (i.e., light).
16.
What is the photosphere of the Sun?
A.
the core of the Sun, where nuclear energy is generated
B.
the region of convecting gases below the visible surface of the Sun
C.
the middle layer of the Sun's atmosphere
D.
the visible "surface" of the Sun
17.
How can we characterize the rotation of the Sun?
A.
differential rotation, with the equator rotating faster than the poles
B.
like a solid body (all parts rotating equally)
C.
in a banded pattern, with alternating bands of fast and slow rotation
D.
differential rotation, with the equator rotating more slowly than the poles
18.
The strength of the magnetic field in a sunspot is estimated from Earth by
A.
measuring the shape of structures seen in the corona above sunspots during solar eclipses.
B.
measuring the Doppler shift of spectral lines of light emitted from above the sunspot.
C.
measuring the size and brightness of the sunspot.
D.
observing the wavelength splitting of atomic spectral lines by the Zeeman effect.
19.
What is the name of a large loop of bright gas extending outward from the edge of the Sun (often seen during total solar eclipses)?
A.
a prominence
B.
a spicule
C.
a plage
D.
a filament
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