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Physics 002 Final Examination 15 December, 2001.
Time allowed: 90 minutes Total: 80 marks

Name:

Student ID:
A




Data table:
1 parsec
3.26 light years

1 parsec
206,265 AU

Speed of light
3 108 m/s

Universal gravitational constant
6.67 10-11 N.m2/kg2

1 Astronomical Unit
1.50 1011 m

Mass of Sun
1.99 1030 kg

Our distance from the center of Milky Way
8,500 pc




Part A Multiple choice (20 marks):

Question
(1)
(2)
(3)
(4)
(5)

Answer









(1)
Which of the following would not be a piece of evidence in support of the general theory of relativity?

A. The precession of the orbit of Mercury around the Sun.
B. The prolonged decay of high-speed muons from space.
C. The change in the orbital period of a binary system of neutron stars.
D.The image of a distant galaxy appearing as a ring around a massive object.
E. A change in the frequency of light as it travels towards the Earth.



(2)
The X-ray pulses from a pulsar change their intensity periodically over 100 days. What is the most probable cause of this periodic variation?

A. Back-and-forth transfer of mass between a red giant and a neutron star.
B. Bursts of carbon explosions.
C. Radiation of gravitational waves by a pair of neutron stars.
D. Synchrotron radiation.
E. The orbital motion of a neutron star in a binary system.



(3)
How does the future of the universe depend on its density?

A. If its density is greater than or equal to the critical density, then the night sky will be darker in the future.
B. If its density is less than the critical density, then the temperature of the cosmic background radiation will eventually rise.
C. If its density is equal to the critical density, then the Hubble constant in the future will be equal to its present value.
D. If scientists find that there is no dark matter in the universe, then the rate of expansion the universe will be faster and faster.
E. None of the above.

(4)
Neglecting small deviations found recently, the uniform and isotropic microwave radiation originating from space is


A.
the emission spectrum of cold interstellar clouds.


B.
emitted from fast-rotating neutron stars.


C.
emitted from accretion disks around black holes.


D.
the background radiation of the Milky Way.


E.
the remnant of blackbody radiation dated back to the Big Bang.





(5)
What are the evidences that active galactic nuclei are due to eruptions of supermassive black holes?

$1: They are common in colliding galaxies.
$2: Doppler shift measurements show that they are surrounded by high-speed gases.
$4: Their X-ray emissions are so strong that it usually takes them several years to fade out.
$8: Their intensity of X-ray emissions is at the same level as the core of our Milky Way galaxy.
After adding the dollar values