Part 1: Multiple choice. Point value of the question is noted in parenthesis.
1.(5) A sound wave travels in air and then hits a lake of water. (The speed of sound in air is
343m/s and the speed of sound in water is 1497 m/s.) If the wavelength in air is a
PW; (5A
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EXAM a.
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SOLUTION TO THIRD EXAM-VERSION 1
1. If the thickness of the lm is t, the dierence in phase between a ray reecting o the
top surface of the lm and one reecting o the bottom surface of the lm is (2n/)2t +
the factor coming from the phase change on reection
Version A
The point value of each question is shown in parenthesis.
1. (10) When a thin soap lm is very thin, we see it as black. How thick (in nm) is the lm
in the region where we see the rst red band? Take the wavelength of red light to be 752
nm and th
Solution to Exam 3A
1. Let the maxima be a distance d apart. If the light from the slits were incoherent, the
amount of energy between the slits would be proportional to 10I0 d where I0 is the intensity
from a single slit. Because the light from the slits
EXAM 2 VERSION B
Multiple Choice Questions. The value of each question is shown in parentheses.
1) (11) At a distance of 2 meters from a 75 Watt light bulb, the amplitude of the electric
eld, in volts per meter, is about
a) 34
b) 3.4
c) 0.34
d) 3.4 102
e)
SOLUTION TO EXAM 2 VERSION A
1.
= v/f = c/(nf ) = 3 108 /[(1.33)(3 102 )] = 7.5 105 .
Ans.d)
2. The (time-averaged) pressure is p = I/c, where I is the (time-averaged) intensity, so the
force is F = IA/c and the equivalent mass is m = IA/cg . With I = 1.
EXAM 2 VERSION A
Multiple Choice Questions. The value of each question is shown in parentheses.
1) (10) The Navy uses extremely low frequency (ELF) electromagnetic radiation of about
300 Hz to communicate with underwater submarines. The wavelength of such
SOLUTION TO EXAM 2 VERSION B
2
1. The intensity is I = 0 E0 c/2 = W/4R2 . So
E=
2W
0 c4R2
1/2
With W = 75, 0 = 8.85 1012 , c = 3 108 , and R = 2 I get E = 34V /m. Ans a)
2. The tangent of Brewsters angle is n2 /n1 where medium 1 is the medium the electrom
Solution to Exam 3A
1. Accounting for the 2cm from eyes to glasses, we have an object at do = 24.98 m and we
want the image to be at di = 2.48m (the minus because the image and object are on the
same side of the lens.) Use 1/f = 1/d0 + 1/di to obtain
f=
d
Version A
Part I. Multiple choice. Point value of the question is noted in parenthesis.
1. (13) The Hydrogen 2p state decays to the 1s ground state and emits electromagnetic
radiation. The frequency of the radiation emitted in this transition is, in Hz,
a
Solution to Final Exam Version A
1. The energy of the nth level of hydrogen is En = E0 /n2 so the energy dierence between
the n = 2 and n = 1 levels is 3E0 /4 and the frequency of the radiation is f = 3E0 /4h. With
E0 = 13.6ev = 2.2 1018 J , f = 2.2 1018
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Print your name (last, first): _
Physics 116A Winter 2011
S. D. Ellis
EXAM 1
Please read the following carefully:
1. Fill in your name (Last, First) and student ID number on your marksense (bubble) sheet. Your name should be given exactly as it appears on
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A small star of mass m orbits a supermassive black hole of mass M.
(a)
Find the orbital speed of the star if its orbital radius is 5R, where R is the Schwarzchild radius (R=2GM/c ).
2
c
(b) Repeat part (a) for an orb
1./3 pointsWalker4 29.P.012.My Notes |
An elementary particle called a pi meson (or pion for short) has an average lifetime of 2.6 10 s when at rest. Suppose that a pion moves with a
8
speed of 0.995c relative to Earth. (a) Find the average lifetime of t
1./2 pointsWalker4 28.P.004.My Notes |
A person driving at v = 18 m/s crosses the line connecting two radio transmitters at right angles, as shown in the figure (d1 = 570 m and d2 = 190 m). The transmitters emit identical signals in phase with each other,
1./1 pointsWalker4 26.P.005.My Notes |
Sunlight enters a room at an angle of = 29 above the horizontal and reflects from a small mirror lying flat on the floor. The reflected light forms a spot on a wall that is d = 1.6 m behind the mirror, as shown in th
1.1/6 points | Previous AnswersWalker4 14.P.071.My Notes |
The human ear canal is much like an organ pipe that is closed at one end (at the tympanic membrane, or eardrum) and open at the other (see the figure below). Suppose that a man's eardrum is of len
1./2 pointsNotesQuestion: Walker4 13.P.050.
A 0.40 kg mass is attached to a spring with a force constant of 33 N/m and released from rest a distance of 5.3 cm from the equilibrium position of the spring. (a) Give a strategy that allows you to find the spe
1./3 pointsNotesQuestion: Walker4 13.P.007.
You rev your car's engine to 2570 rpm (rev/min). (a) What is the period and frequency of the engine? period frequency s Hz
(b) If you change the period of the engine to 0.141 s, how many rpms is it doing? rpm
2.