Physics Unit33: Astrophysics and Cosmology

1#

The appearance of the great range of brightneymojw/f,-jqq az g/6 z2/ey 1css among stars 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 most stars depends on tc*05o 590wlcmz uwn xhq;rd j3he (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 stars are colored blue, orange, red, and n1x9h+vpf sh f-bwnyizb6.0 . yellow. What is their rank from coole1bsv.9p+f0fz.- xyh6w nnibh st 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 diagram shows stars o,/r a.jwsvw tb5. 65bt a/e)xzqi*zxon 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 h7.;jl znv)h tthat of the Sun is about 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 will col3a,//l;brbwzyo r 0m jlapse into a white dwarf) is, if the mass of our Sun is M, abjrol/, a/m w 3z0b;ybrout (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 thought to always 2c/l47fa/w) ip uor kzresult 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 spin*h co r jouo2l)q80voriqk(3)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 equivag6b0avle y.z3g. p w9rlence. (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 blandk(z6 m, rvdo-r4mf*ck hole is that radial distance from the center of a sphere within which not even light can escape. It was first discovered mathematically by Schwarzschild in 1916 after Einste*6m-nrm(z 4kfdd,ov rin 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 wavelz8 k 14lhw4qduength in the visible, and1l wq4kzd 8h4u the source is moving away from us, the color of the light appears to us to be shifted toward 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 radiation3)weerzdg2l) 0w. b fu corresponds 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 u*;s gmi/ th:9*cp1 qvd t(txzbrightness at Earth ($1.5 \times 10^{8} \; km$ 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 luminositu n8a6d:hamk5 y equal to that 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 radius of vpt -qw(h5/fl9e2o0 3 j.xespaoztm +$1.5 \times 10^{8} \; km$. 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 has a mean radiuw,)vx dmskd4 52 abyvprjo18 5s 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 nearest sta(wa,zb+oep/a r ao(/a bepw+za ,t 4.3 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 brightness of wmrbm2)wf )e1r v54j21lwfk :bcl jg2a 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 un(ole s /3fh pvv(g:oo++rlg4 lj)e5 ddiverse is 1/H, where H is the Hubble constant. Taking H = 20 km/s/Mly, estimate 5g (3oo +4lv/e(lrsl:dej)vg dfhpo+the age of 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 movin 4rbzqa8-x0 edg away from us at 1.0% of the speed of light, how far away is it 0r -q48zeaxdbfrom 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 10 billion light-1 q4 ezx6li)xg 9z6aphyears 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 6.p xu 214qgpxb56 nm line in the spectrum of a star which is 100 million lig4 2x1qgupxb.p ht-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 dcem,18kozfyqmi/ 46)mlpfc dk k+p3c35:a iBang, the temperature of the universe was about 1013 K. What energy (in e3pfkidla )mz/5o3m6ykc dm:k1 ,fcpi +c8 4qeV) does this correspond to? (1.0 分)

A. $1 \; keV$

B. $1 \; MeV$

C. $1 \; GeV$

D. $1 \; TeV$

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