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- 1.
- A phase synchronized linear array of
6
radiotelescopes
40
km apart operates on a wavelength of
25
cm.
- (a)
- What angular separation of distant sources can it resolve?
Please give your answer in arc seconds.
- (b)
- If it ``looks at'' a source
800
light years away, what is the source linear resolution
compared to the Sun-Jupiter distance?
- 2.
- A sound absorbing straight wall is 20 m high
and 100 m long; at its centre, ground level, is
a 1.2
m wide open doorway. You are
32
m straight in front of the doorway when a whistle
55
m directly behind the doorway begins to blow at
900
Hz.
How far along a line parallel to the wall
(and passing through your present position)
must you move before the sound first becomes imperceptible?
- 3.
- Consider a series of
10
equal slits, each
0.004
cm wide, arrayed in a straight line with equal spacing so that
0.22
cm separates the centres of the first and last slits.
This configuration is illuminated from behind
by a distant source of light of wavelength 0.546 micron [m].
- (a)
- How many major intensity peaks will you see in the
entire pattern displayed on a wide screen 20 m away
before the pattern first fades away laterally?
- (b)
- How far apart and how wide (in mm) are the
principal maxima near the centre of the screen?
[``principal''
``major'']
- 4.
- It is claimed that a satellite carries a camera
capable of discerning details as small as
12
cm across at a distance of
200
km, using visible light of wavelength
0.55 m.
What must be the minimum diameter of the camera lens?
- 5.
- Two loudspeakers
60
cm apart each emit
40
watts of
1800
Hz sound uniformly over a conical region representing
1/9
of the full sphere of possible directions.
Imagine a line AB parallel to the line joining the speakers, but
28
m distant from the speakers.
Then suppose that you are 4 m off the system's symmetry axis
(bisecting the line joining the speakers) on line AB.
- (a)
- If only one speaker is operating, what is the sound intensity
(in watts/m2) at your location?
- (b)
- If both speakers are on, and in phase,
what sound intensity do you receive?
Next: INTERFERENCE & DIFFRACTION II
Up: Old P120 Homework Questions
Previous: INTERFERENCE