=========================preview======================
(PHYS002)mid2a_s01.pdf
Back to PHYS002 Login to download
======================================================
Physics 002 Midterm 2 19 April, 2001.
Time allowed: 80 minutes Total: 80 marks


Name:

Student ID:
A




Part A Multiple choice (5 marks each):

(1) Refer to Fig. 1. If an M0 giant star has an apparent visual magnitude of +6.3, its distance from the Earth is closest to:
A. 10 pc
B. 50 pc
C. 200 pc
D. 600 pc
E. 1000 pc Ans. _____

(2) Compare the evolution of a 25 solar-mass main-sequence star and that of the Sun.
A.
Both stars will undergo the CNO cycle towards the end of the main-sequence stage.


B.
Both stars will experience a helium flash.


C.
Both stars will produce a core of carbon and oxygen at the end of the main-sequence stage.


D.
Both stars will produce neutrinos during the main-sequence stage.


E.
Both stars will die as white dwarfs. Ans. _____




(3) If an astronomer discovers a new star, what measurements can let him determine its position in the HR diagram?
A.
Apparent magnitude, stellar parallax, spectral type


B.
Apparent magnitude, Doppler shift, spectral type


C.
Luminosity class, Doppler shift, collisional broadening


D.
B-V index, spectral type, apparent magnitude


E.
Stellar parallax, spectroscopic parallax, luminosity class Ans. _____




(4) The Chandrasekhar limit exists for white dwarfs because
A.
When electrons are heated more and more, their pressure will increase further and further.


B.
When electrons are confined more and more, their momenta will increase further and further.


C.
When electrons are heated more and more, they become more and more degenerate.


D.
When electrons become more and more degenerate, their momenta will increase further and further.


E.
When the pressure-temperature thermostat becomes less and less effective, the electrons are confined more and more.

Ans. _____



(5) Refer to the HR diagram in Fig. 2. Which of the following is correct?
A.
E produces more energy per surface area than A.


B.
F can be involved in a future supernova.


C.
G can have the same mass as A.


D.
There are more stars like G than there are stars like D.


E.
None of the above is correct. Ans. _____




(6) Which two of the following can be observed during star formation?
I.
Jets of gas blowing away in opposite directions from a star.


II.
Infrared sources within a giant molecular cloud.


III.
Ultraviolet sources within a nebula.


IV.
Expanding gas cloud surrounding a neutron star.



A.
I and II


B.
II and III


C.
III and IV


D.
I and IV


E.
III and I Ans. _____




(7) What is true of white dwarfs?
A.
They can be made of a combination of helium, oxygen and/or carbon.


B.
No electrons are present in a white dwarf because the force of gravity is too large.


C.
They contract as they cool dow