Physics Unit33: Astrophysics and Cosmology

1#

The appearance of the great range of brightness among starsxrz)z7c.6b jf7d q xi3 is due to (1.0 分)

A. the differences in the amount of light different stars emit.

B. the differences in the distances of stars from us.

C. both of the given answers

D. none of the given answers

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2#

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The absolute luminosity for 4 - :36dzczlnkb,jzrwmost stars depends on the (1.0 分)

A. radius of the star.

B. cross sectional area covered by the star.

C. volume covered by the star.

D. the mass of the star.

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3#

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Four different main-sequence stamwq:z0s- zinzbz +*3ars are colored blue, orange, red, and yellow. Whaabiz -mnz * :sz0zqw3+t is their rank from coolest to hottest? (1.0 分)

A. blue, yellow, orange, red

B. orange, blue, yellow, red

C. red, orange, yellow, blue

D. red, yellow, orange, blue

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4#

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A Hertzsprung-Russell diqsxxko+/ u1 /;nsg (aw4 piz;aagram shows stars on a plot of (1.0 分)

A. apparent brightness vs. temperature.

B. luminosity vs. temperature.

C. luminosity vs. distance.

D. magnitude vs. apparent brightness.

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5#

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A white dwarf star with a mass equal to that of the Sun is akatj 1.o0gd9b bout the size of (1.0 分)

A. the Sun.

B. the Earth.

C. a basketball.

D. a baseball.

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6#

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The Chandrasekhar limit of stellar mass (below which a star wia i4 b;da8* lrzz wag4fe+i/a*ll collapse into a white dwarf) is*aa 8*;b f4+aa4 zr/iwgeldiz , if the mass of our Sun is M, about (1.0 分)

A. 0.8 M.

B. 1.2 M.

C. 1.4 M.

D. 1.9 M.

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7#

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Supernovas are thoughtw xy6++ukockbt- e :9+4vpolg to always result in (1.0 分)

A. neutron stars.

B. red giant stars.

C. regular stars like our Sun.

D. white dwarfs.

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8#

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Black holes (1.0 分)

A. are holes in space, devoid of matter.

B. are predicted by Einstein's special theory of relativity.

C. are the collapsed remnant of stars.

D. cannot be detected in binary star systems.

E. are a violation of Einstein's general theory of relativity.

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9#

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Pulsars are rapidly spinyob0fk)(pz ex4cx k2*pdpx4/h csi8/ning (1.0 分)

A. regular stars like our Sun.

B. red giant stars.

C. neutron stars.

D. white dwarfs.

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10#

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State Einstein's principle of equ9b(mzzl o f6w1 0whta8ivalence. (1.0 分)

该题自我估分: (必填) (满分:1.0分)

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11#

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The Schwarzschild radius of a ind1c( 8z +yhj+/ipm wblack hole is that radial distance from the center of a sphere within which not even light can escape. It1jh p/(mync zi8i++dw was first discovered mathematically by Schwarzschild in 1916 after Einstein published his general relativity theory. It can be calculated from a star's mass M as: $R = 2GM/c^2$. Take the radius of both stars A and B as the Schwarzschild radius. If the mass of star A is twice as much as the mass of star B, the average density of star A, compared to star B will be (1.0 分)

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12#

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When a distant source emits light of a particular wavelengt-w7g yj;d 54laq 0tizhh in the visible, and the source is moving away from us, the color of the light appears to us to be shifted toward tqw4a-dl0 gz7;5yjh i the (1.0 分)

A. red end of the visible spectrum.

B. blue end of the visible spectrum.

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13#

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The cosmic background radiation chi lf hi- ioqmb,;/m0my t(y5wrl+2 w:orresponds to a temperature of about (1.0 分)

A. 1.4 K.

B. 2.7 K.

C. 3.0 K.

D. 3.3 K.

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14#

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The Sun has apparent brightness at Earth c7e9:d5m +:zjhim cq k($1.5 \times 10^{8} \; km$ away) of B. What would be the apparent brightness of the Sun at Pluto, which is $6.0 \times 10^{9} \; km$ from the Sun? (1.0 分)

A. $0.25 \; B$

B. $0.063 \; B$

C. $0.025 \; B$

D. $0.00063 \; B$

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15#

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A star has absolute luminosity equal to thajjs *w11 g-xkut of the Sun ($1.5 \times 10^{8} \; km$ from the Earth) but is 10 pc away from the Earth. By what factor will it appear dimmer than the Sun? (1.0 分)

A. $2 \times 10^{-9}$

B. $2 \times 10^{-11}$

C. $2 \times 10^{-13}$

D. $2 \times 10^{-15}$

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16#

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The Earth's orbit has a mean radiuq/ (vdd8xfs n+s of $1.5 \times 10^{8} \; km$. Over a six-month period, the apparent position of a particular star varies by $0.00014^{\circ}$ due to parallax. How distant is the star, in km? (1.0 分)

A. $1.2 \times 10^{11} \; km$

B. $1.2 \times 10^{14} \; km$

C. $1.2 \times 10^{17} \; km$

D. $1.2 \times 10^{20} \; km$

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17#

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The Earth's orbit haie*0oyfj (pte6e 5 yd5 wdkp5*s a mean radius of $1.5 \times 10^{8} \; km$. Over a six-month period, the apparent position of a particular star varies by $0.00014^{\circ}$ due to parallax. How distant is the star, in ly? (1 ly = $9.46 \times 10^{15} \; m$) (1.0 分)

A. $0.13 \; ly$

B. $1.3 \; ly$

C. $13 \; ly$

D. $130 \; ly$

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18#

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What is the parallax angle for Proxima Centauri, which is Earth's ne,44uie w squfog+4p:k arest star at 4.3ougiw:fs4uep4 k+,q4 ly? (1.0 分)

A. $1.2 \times 10^{-14} \; degrees$

B. $2.1 \times 10^{-4} \; degrees$

C. $1.2 \times 10^{-7} \; degrees$

D. $2.1 \times 10^{-7} \; degrees$

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19#

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The apparent brightn:9d-0:ehap stlz nxod ;i2 hj1ess of a star is $1.0 \times 10^{-12} \; W/m^{2}$ and the peak wavelength is 600 nm. Estimate its distance from us. (1.0 分)

A. $0.90 \; pc$

B. $9.0 \; pc$

C. $90 \; pc$

D. $900 \; pc$

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20#

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It can be shown that the approximate age of the universe is 1/H, where H m-w4hxnv4on tm7j:e 7is the Hubble constant. Taking H = 20 km/s/Mly, estimate the age -77:ewjmh nm44nx t voof the universe, in years. (1.0 分)

A. 15 thousand years

B. 15 million years

C. 15 billion years

D. 15 trillion years

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21#

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If a galaxy is moving away qj:c1 8is*o 4cuji5v is*aejq3*o8ly 7fq- ar from us at 1.0% of the speed of light, how far away is it fro*74si1r-3a8osccejj*5jiuqavi qy* q l8 f:om us? (1.0 分)

A. 200 ly

B. 200 thousand ly

C. 200 million ly

D. 200 billion ly

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22#

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Estimate the speed of a galaxy that is 10v :lx8x map f*+hnb y-zuu+h.4 billion light-years away. (1.0 分)

A. $0.1 \; c$

B. $0.3 \; c$

C. $0.5 \; c$

D. $0.7 \; c$

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23#

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Estimate the observed wavelength for the 656 nm line in the spectrwua;l k:a rnj5 dv;2.tum of a star which isaw:5 ak;n 2v utl;dj.r 100 million light-years from us. (1.0 分)

A. $653 \; nm$

B. $656 \; nm$

C. $659 \; nm$

D. $692 \; nm$

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24#

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About 1 ms after the Big Bwh azcf v)f2gsfkq::7rd3.g 9ang, the temperature of the universe was about 1013 K. What energy (in eV) dgfcd9r. s 32)f::kf qhgvawz7 oes this correspond to? (1.0 分)

A. $1 \; keV$

B. $1 \; MeV$

C. $1 \; GeV$

D. $1 \; TeV$

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