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PHYSICS DEPARTMENT
PHY 2054
Final Exam [CJ Ch. 25{27]
Name (print):
05 August 1999
Signature:
On my honor, I have neither given nor received unauthorized aid on this examination.
YOUR TEST NUMBER IS THE 5-DIGIT NUMBER AT THE TOP OF EACH PAGE.
DIRECTIONS
(1) Code your test number on your green answer sheet (use 76{80 for the 5-digit number). Code your name
on your answer sheet. Darken circles completely (errors can occur if too light). Code your student number
on your answer sheet.
(2) Print your name on this sheet and sign it also.
(3) Do all scratch work anywhere on this exam that you like. At the end of the test, this exam printout is to be turned
in. No credit will be given without both answer sheet and printout with scratch work most questions demand.
(4) If there is no answer close enough to be correct, the correct answer is to leave the question blank. You should not
expect many of these.
(5) Blacken the circle of your intended answer completely, using a number 2 pencil. Do not make any stray
marks or the answer sheet may not read properly.
(6) Good luck!!!!
Have fun!!!
>>>>>>>>BEFORE YOU FINISH <<<<<<<<
Make sure your test number is coded in correctly. Your test score will be posted under this number, so write it down and
take it with you Hand in the exam and the green answer sheet separately.
Useful (??) Constants:
visible light is 750 nm (red) { 380 nm (violet)
electron charge = ¡1:6 £ 10¡19 C
V=volt
N=newton
electron mass = 9:11 £ 10¡31 kg
J=joule
m=meter
W=watt ¹ = \micro-" = 10¡6
A = ampere \pico" = 10¡12 n = \nano" = 10¡9 m = \milli" = 10¡3 proton mass = 1:67 £ 10¡27 kg
c = 3 £ 108 m/s
1. A penny placed on the °oor is covered by a smooth- sided transparent block of ice (refractive index 1.31) that is 40
cm thick. Viewed from above [rays approximately perpendicular to the ice surface] the image of the penny will be:
(1)
(2)
(3)
(4)
(5)
virtual,
virtual,
real, 31
real, 39
real, 40
31 cm below top of ice block
39 cm below top of ice block
cm below top of ice block
cm below top of ice block
cm below top of ice block
2. The rectangular metal tank shown is ¯lled with an unknown liquid. The observer, whose eye is level with the top of the tank, can just see corner E. The
index of refraction of this liquid is:
(1) 1.25
(2) 1.33
(3) 1.50
(4) 1.75
(5) 1.67
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3. A light ray traveling in air is incident at 30 degrees on a piece of optical material. The angle of refraction for the ray
within the material is 21 degrees. What is the critical angle (in degrees) for this material?
(1) 46
(2) 54
(3) 30
(4) 21
(5) 24
4. A lens produces an erect image of a dime that is twice the diameter of the dime. If the image is is 2.84 cm from the
lens, what is the focal length of the lens?
(1) +2.84 cm
(2) ¡2:84 cm
(3) +0.95 cm
(4) ¡0:95 cm
(5) +1.06 cm
5. The near point of an eye is at 100 cm. What is the power of the lens (in diopters) that will permit this person to see
objects located at 25.4 cm from the eye?
(1) +2.94
(2) 2:94
(3) +3.94
(4) ¡3:94
(5) +34
6. A 2-cm-tall object is placed 400 mm from a converging lens, which is observed to form an image three times the size
of the object. To make the image ¯ve times the size of the object, the object-lens distance (in mm) must be changed
to:
(1) 360
(2) 540
(3) 600
(4) 720
(5) 960
7. When a beam of monochromatic light traveling in air enters a glass block it ordinarily undergoes a change in:
A. coherence
B. wavelength
C. frequency
D. speed
(1) B,D
(2) A,D
(3) C,D
(4) D only
(5) A,C,D
8. A frog sits 40cm from a lens of focal length +20 cm. The frog now hops out along the axis to 1.0 m from the lens.
The frog's image moves (with respect to the lens) from
(1) 40cm to 25 cm
(2) 40cm to 100cm
(3) 20cm to 40 cm
(4) 40cm to 20cm
(5) none of these
9. Two light waves are coherent if:
(1)
(2)
(3)
(4)
(5)
their phase di®erence is constant
their frequencies are identical
their wavelengths are the same
their amplitudes are identical
the di®erence between their frequencies is invariant
10. A soap (water!) ¯lm in air has refractive index 1.34 and is 550 nm thick. What wavelengths of visible light (in nm)
are not re°ected from it when it is illuminated from directly above by sunlight?
(1) 737, 491
(2) 550, 367
(3) 550
(4) 1470
(5) none
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11. Light from a small region of a 100-W incandescent bulb passes through a yellow ¯lter and then serves as the source for
a Young's double-slit interference experiment. Which of the following changes would cause the interference pattern
to be more closely spaced?
(1)
(2)
(3)
(4)
(5)
Use a blue ¯lter instead of a yellow ¯lter
Use a 10-W bulb
Use a 500-W bulb
Move the bulb closer to the slits
Move the slits closer together
12. Light of a given wavelength falls normally on a certain di®raction grating. The ¯rst order maximum is observed on
an adjacent screen and is found to appear at an angle of 25 degrees. The second-order maximum will appear on this
screen at what angle (in degrees)?
(1) 58
(2) 50
(3) 42
(4) 25
(5) 75
13. A clock on a passing spaceship is observed from earth with a powerful telescope. During a 60.0 s time interval on
earth, 52.0 s are seen to elapse on the spaceship's timepiece. What is the spaceship's speed, relative to earth?
(1) 0.5c
(2) 0.87c
(3) 0.93c
(4) 0.37c
(5) 0.25c
14. An electron is moving at 0.6c. If we calculate its kinetic energy using (1=2)mv 2 , we get a result which is:
(1) about 25% too low
(2) correct
(3) twice the correct value
(4) about 1% too low
(5) just half enough
15. If the kinetic energy of a particle is equal to its rest energy then its speed must be:
(1) 0.87c
(2) 0.50c
(3) 0.25c
(4) c
(5) can't calculate it without knowing the mass