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PHYSICS 002 Midterm 1 Solution
Time allowed: 70 minutes
11 March 2003
Total: 70 marks
A
Part A: Short questions (18 marks, 2 marks each)
The above figure shows the positions of the Earth and the Moon, as viewed from above the North Pole on 1 March. A to H represent 8 locations on the surface of the Earth. (The distance between Earth and Moon is not drawn to scale.)
Answer
1
What is the local time in location F?
9 am
2
What is the angle of elevation of the Moon as observed from location B? (The angle of elevation of an object is the angle its direction makes with the horizon.)
45o
3
At which location is the Moon rising from the East?
G
4
What is the phase of the Moon as observed from location A?
Quarter*
5
As observed from location A, is the round edge of the bright surface of the Moon facing East or West?
West
6
On 8 March, what is the angle of elevation of the Moon as observed from location D?
45o
* In fact, the quarter phase of the Moon is observed from any location where the Moon is visible.
* Answering first quarter is correct, but answering third quarter is wrong.
North Pole To Sun
Moons orbit
Earth To Sun and Leo
B
Betelgeuse is a star with a luminosity 60,000 times that of the Sun. Its surface temperature is 3,200 K. (The surface temperature of the Sun is 5,800 K.)
Give your answer to 2 significant figures.
Answer
7
What is the wavelength of the peak intensity in the radiation of Betelgeuse? Give your answer in nm.
940 nm
8
What is the flux from Betelgeuse in units of the solar flux?
0.093
9
Calculate the radius of Betelgeuse in units of solar radius.
800
7. Using Wiens law, wavelength of the peak intensity = 3,000,000/3,200 = 938 nm 940 nm.
8. Using Stefan-Boltzmanns law, the flux = (3,200/5,800)4 = 0.093 solar flux.
9. Since L T4R2,
. Hence
.
Part B: True or false questions (16 marks, 2 marks each)
True
False
1
During a total solar eclipse, the corona of the Sun can be observed.
2
On the Earth surface, telescopes with diameters 2 m have the same resolving power as those with diameters 5 m.
3
To an observer on Earth, both Venus and Mars appear largest at the crescent phase.
4
When starlight passes through an interstellar cloud, the detected light has an emission spectrum.
2. The resolving angle of the 2 m telescope limited by diffraction = 11.6/200 = 0.058 arc second.
The resolving angle of the 5 m telescope limited by diffraction = 11.6/500 = 0.023 arc second.
However, the resolving angle limited by atmospheric seeing is 0.5 arc second, which is greater than both of these values. Hence the resolving angle of both telescopes is 0.5 arc second.
3