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PHYS 1112 In-Class Exam #1B Tue. Feb. 8, 2011, 11:00am-12:15pm

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PHYS 1112 In-Class Exam #1B Tue. Feb. 8, 2011, 11:00am-12:15pm
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
PHYS 1112 In-Class Exam #1B
Tue. Feb. 8, 2011, 11:00am-12:15pm
This is a closed-book, closed-notes exam, but you are permitted to bring and use a clean
copy of the official Formula Sheet for this exam, which you should have printed out from the
PHYS1112 web page.
The exam consists of 12 multiple-choice questions. Each question is worth one raw score
point. There will be no penalty for wrong answers. No partial credit will be given. I
recommend that you read all the questions at the start so that you can allocate your time
wisely. (Answer the easy questions first!)
You may use a scientific calculator for arithmetic only; your calculator must be non-graphing,
non-programmable, and non-algebraic. You are not allowed to share your calculator. The
use of cell phones, pagers, PDAs, or any other electronic devices (besides calculators) is
forbidden. All such gadgets must be turned off and put away; distractions caused by these
devices will not be tolerated.
• Do not open the exam until you are told to begin.
• Make sure the scantron sheet has your name and your UGA Card ID (810-...)
number filled in. Make sure you also have entered your name, UGA Card ID number
and signature on the exam cover page (this page!) below.
• At the end of the exam period you must hand in both your scantron sheet and this
entire exam paper, with cover page signed and with your name and UGA Card ID
(810-...) number filled-in.
• Your exam will not be graded, and you will receive a score of zero, if you do not
hand in both a properly filled in scantron sheet and this entire exam paper with
properly filled-in and signed exam cover page.
• You have until the end of the class period (i.e. until 10:45am for Period 2 Class, until
12:15pm for Period 3 Class) to finish the exam and hand in the required exam materials
described above.
By signing below, you indicate that you understand the instructions for this exam and agree
to abide by them. You also certify that you will personally uphold the university standards
of academic honesty for this exam, and will not tolerate any violations of these standards by
others. Unsigned exams will not be graded.
Name (please print):
UGACard ID (810-...) #:
Signature:
1
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
WORKSPACE
2
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
Conceptual Problems
Problem 1: A convergent lens L, a concave mirror M and two small lightbulbs B and
C, are rigidly mounted in two empty water tanks, as shown below. From B and C, L and
M produce images B 0 and C 0 , respectively. What happens to the locations of B 0 and C 0
when both tanks are completely filled with water, compared to their original locations in the
empty tanks? (Hint: Think about the focal lengths of L and M .).
L B’ (A)
(B)
(C)
(D)
(E)
B0
B0
B0
B0
B0
M B C’ C moves towards L and C 0 moves towards M .
moves towards L and C 0 moves away from M .
moves away from L and C 0 moves towards M .
moves towards or away from L and C 0 does not move.
does not move and C 0 moves towards or away from M .
Problem 2: UGA waves (we didn’t cover those in class, but they do obey Snell’s law!) have
a speed of wave propagation vA = 522m/s in apple juice and vB = 2097m/s in butter milk.
Also, assume that sin(14.414o ) = 522/2097 . A narrow beam of UGA waves striking a
flat horizontal interface between apple juice and butter milk, with the apple juice above
and the butter milk below the interface
(A) will not undergo total internal reflection if incident from above the interface with
an angle of incidence of 29.0o ;
(B) will always have an angle of refraction not exceeding 14.414o if the beam is incident
from above the interface without total internal reflection;
(C) will undergo total internal reflection if incident from above the interface with an
angle of incidence of 8.5o ;
(D) will undergo total internal reflection if incident from below the interface with an
angle of incidence of 29.0o ;
(E) will have an angle of refraction greater than the angle of incidence if the beam is
incident from above the interface without total internal reflection.
3
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
Problem 3: Two identically shaped solid blocks, S and T , made from the two different
transparent materials, are immersed in the same liquid L. A ray of light strikes each block
at the same angle of incidence, as shown. According to the figure below, what is the relative
magnitude of the indices of refraction of the solid blocks, nS and nT , and liquid, nL ?
L
L
S
(A)
(B)
(C)
(D)
(E)
nS
nT
nS
nL
nT
T
< nL < nT ;
< nS < nL ;
< nT < nL ;
< nS < nT ;
< nL < nS .
Problem 4: If a virtual object (d < 0) is presented to a divergent mirror (f < 0), at an
absolute distance |d| more than twice, the absolute focal length |f |, i.e., |d| > 2|f |, then the
image is
(A)
(B)
(C)
(D)
(E)
virtual, inverted and enlarged in height relative to the virtual object
virtual, inverted and reduced in height relative to the virtual object
virtual, erect and reduced in height relative to the virtual object
real, inverted and enlarged in height relative to the virtual object
real, erect and enlarged in height relative to the virtual object
4
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
Numerical Problems
Problem 5: Visible light has a range of wavelengths from 400nm (violet) to 700nm (red) in
vacuum. A beam of electromagnetic waves with a frequency of 681.8THz in air travels from
air into water, with indices of refraction nAir = 1.00 and nWater = 1.333. To an under-water
observer, the beam while traveling in water will
(A) have a wavelength of 330.1nm, have the same frequency as in air, and be visible to
the human eye;
(B) have a wavelength of 330.1nm, have a frequency of 908.8THz, and be invisible to the
human eye;
(C) have a wavelength of 586.5nm, have the same frequency as in air, and be visible to
the human eye;
(D) have a wavelength of 440.0nm, have a frequency of 511.5THz, and be visible to the
human eye;
(E) have a wavelength of 330.1nm, have the same frequency as in air, and be invisible to
the human eye.
Problem 6: The state highway patrol radar guns send out a a microwave frequency of
16.20GHz. At a radar speed trap, the receiver on the radar gun measures the frequency of
the microwave reflecting from your car, and finds it to be 3950Hz lower than the original
frequency sent out by the gun. How fast were you going and in which direction?
(A)
(B)
(C)
(D)
(E)
Traveling
Traveling
Traveling
Traveling
Traveling
towards the radar gun at 73.1m/s.
away from the radar gun at 73.1m/s
towards the radar gun at 36.6m/s.
away from the radar gun at 36.6m/s
away from the radar gun at 18.3m/s
5
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
Problem 7: Two plane mirrors intersect at an angle θ = 63o , as shown here:
β q
_
e
A light ray is incident on the bottom, horizontal mirror at an angle of α = 25o . What is the
angle of reflection, β, for the 2nd reflection, occuring at the slanted mirror?
(A)
(C)
(B)
(D)
(E)
101o
88o
63o
50o
38o
Problem 8: Two laser beams are passing from air through a thick glass wall into a chemical reactor tank filled with water, as shown below. The glass wall has two parallel planar
surfaces. Both beams exit the wall at the same point, beam 1 normal to the wall, beam 2 at
an angle β = 50o to the wall. The two beams’ points of entry into the wall are y = 16.6cm
apart and beam 2 travels a distance z = 34cm inside the glass. Air and water have indices
of refraction nAir = 1.00 and nWater = 1.333, respectively. What is the index of refraction of
the glass?
beam 2 beam 1 β beam 1 y beam 2 (A)
(B)
(C)
(D)
(E)
2.09
1.95
1.75
1.32
1.01
6
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
Problem 9: A candle placed 50.00cm to the left of a curved mirror produces an image
20.00cm to the right of the mirror. What is the spherical radius of the mirror and where is
the center C of that sphere?
(A)
(B)
(C)
(D)
(E)
−33.3cm,
−66.6cm,
−66.6cm,
−33.3cm,
+28.6cm,
C
C
C
C
C
to
to
to
to
to
the
the
the
the
the
left of the mirror;
left of the mirror;
right of the mirror;
right of the mirror;
left of the mirror.
Problem 10: If the candle in Problem 9 is 25.0cm tall its image produced by the mirror
will be
(A)
(B)
(C)
(D)
(E)
real, inverted and 10.0cm tall;
virtual, erect and 10.0cm tall;
virtual, inverted and 10.0cm tall;
virtual, erect and 62.5cm tall;
real, inverted and 62.5cm tall.
Problem 11: A convergent lens (Lens1) is placed to the right of a small sand grain and to
the left of a divergent lens (Lens2). Lens 1 produces a real image of the grain 6.81cm to the
right of Lens2. Lens2 has a focal length f2 = −7.83cm. How far from Lens2, and to which
side of it, is the final image of the sand grain, produced by Lens2? Is this final image virtual
or real?
(A)
(B)
(C)
(D)
(E)
Virtual image, 3.6cm to the left of Lens2.
Virtual image, 3.6cm to the right of Lens2.
Real image, 3.6cm to the right of Lens2.
Real image, 52.3cm to the left of Lens2.
Real image, 52.3cm to the right of Lens2.
7
Physics 1112
Spring 2011
University of Georgia
Instructor: HBSchüttler
Problem 12: A telescope produces a final image of a skyscraper (as seen through the
eyepiece) which appears to be 4.9cm tall and located 55.0cm from the eyepiece on the
incoming side of the eyepiece lens. Assume the skyscraper is at a distance of 9.0km and
160m tall. What is the angular magnification achieved with the telescope, compared to
viewing the building from the actual 9.0km (reference) distance without telescope?
(A)
(B)
(C)
(D)
(E)
∼ 5.0
∼ 8.6
∼ 12.4
∼ 16.8
∼ 25.3
8
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