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Physics 1212 Exam #1 Instructions:

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Physics 1212 Exam #1 Instructions:
Physics 1212 Exam #1
Tue, 10 February 2015
Name:
Physics 1212
Exam #1
Instructions:
This is a closed-book, closed-notes exam. You are allowed to use a clean print-out of your
formula sheet, a non-progammable, non-algebra scientific calculator, and a ruler. Do not
write on your formula sheet
There is space after each question to show your work; if you need more space, you may use
the back of the page, or request more paper. Please clearly indicate where your work for
each problem is. Underline or draw a box around your final answer.
The exam consists of four sections. Read all the questions at the start so that you can
allocate your time wisely. Do easy ones first!
You may not share your calculator. The use of cell phones or any other electronic devices (besides calculators) is prohibited. All such gadgets must be turned off and put away
throughout the exam.
• Do not open the exam until told to begin.
• You have the entire lab/class period to finish the exam.
• Put your last name on every page of the exam.
• You must provide explanations and/or show work legibly to receive full credit for
Sections III and IV.
• Make sure that your answers include appropriate units and significant digits. (Note:
For intermediate steps in your calculation, it’s best to carry around more significant
digits.)
• Assume that the index of refraction of air is the same as for a vacuum, unless otherwise
stated.
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’s standards
of academic honesty for this exam, and will not tolerate any violations of these standards by
others. Unsigned exams will not be graded.
Signature:
UGACard #:
c 2015 University of Georgia. Unauthorized duplication or distribution prohibited.
Copyright Physics 1212 Exam #1
Tue, 10 February 2015
Section
Score
I
/20
Name:
II
/10
III
/35
IV
/35
I: Multiple-Choice Questions (20 points)
For each question below, choose the single best response and write the corresponding
capital letter in the box provided. There is no penalty for guessing the wrong answer.
1. UGA waves weren’t covered in class, but they do obey Snell’s law! They have a speed
of wave propagation vA = 2097m/s in apple juice and vB = 522m/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 always have an angle of refraction not exceeding 14.414o if the beam is
incident from below the interface without total internal reflection;
B. will undergo total internal reflection if incident from above the interface with
an angle of incidence of 8.5o ;
C. will not undergo total internal reflection if incident from below the interface
with an angle of incidence of 29.0o ;
D. will not undergo total internal reflection if incident from above 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.
2. A real object is placed in front of a converging lens, at a distance smaller than the
focal length. When the object is moved slightly away from the lens, without crossing
the focal point, in which direction does the image move or change its size?
A.
B.
C.
D.
E.
The image moves closer to the lens.
The image position doesn’t change.
The image moves farther away from the lens.
The image (lateral) size shrinks.
Not enough information is given.
c 2015 University of Georgia.
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Physics 1212 Exam #1
Tue, 10 February 2015
Name:
3. Visible light has a range of wavelengths from 400nm (violet) to 700nm (red) in vacuum.
A beam of electromagnetic waves with a frequency of 714.3THz 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 420.0nm, have a frequency of 535.9THz, and be visible to
the human eye;
B. have a wavelength of 315.1nm, have the same frequency as in air, and be visible
to the human eye.
C. have a wavelength of 559.9nm, have the same frequency as in air, and be visible
to the human eye;
D. have a wavelength of 315.1nm, have the same frequency as in air, and be invisible
to the human eye;
E. have a wavelength of 315.1nm, have a frequency of 952.2THz, and be invisible
to the human eye;
4. Two identically shaped solid blocks, S and T , made from 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
nT
nS
nL
T
< nT < nL ;
< nL < nS ;
< nS < nL ;
< nL < nT .
< nS < nT ;
c 2015 University of Georgia.
Copyright 3
Physics 1212 Exam #1
Tue, 10 February 2015
Name:
II: Draw a Ray Diagram (10 points)
A virtual object is positioned to the left of a divergent lens, at a distance from the lens
which is less than the absolute value of the lens’s focal length. Use a ruler to draw a clean
ray diagram for the formation of the image, showing at least two of the principal rays, the
lens and both its focal points, the object and the image, all of them clearly labeled. Also
clearly label the incoming and the outgoing side of the lens. Is the image real or virtual?
c 2015 University of Georgia.
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Physics 1212 Exam #1
Tue, 10 February 2015
Name:
III: Refraction in a Prism (35 points)
A light beam enters a solid, transparent prism, with an index of refraction nP = 1.35, through
the planar front surface, A, at an angle α = 19o , measured from A. The beam emerges from
the prism through the planar top surface B, at an angle β, measured from B, as shown
below. In parts (a) and (b), assume the prism is immersed in air, with nAir = 1.00.
(a) Find β!
(b) What is the minimum value of α required for the beam to undergo total internal
reflection at B?
(c) If the prism is immersed in some unknown transparent liquid (not water!), the angle
β changes to 87o , assuming the same α = 19o as in part (a).
What is the index of refraction of the liquid?
Hints: sin(90o − x) = cos(x),
cos2 (x) + sin2 (x) = 1,
sin(x)/ cos(x) = tan(x).
c 2015 University of Georgia.
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Physics 1212 Exam #1
Tue, 10 February 2015
Name:
IV: Astronomical Telescope (35 points)
In an astronomocal telescope, an objective lens of +105.0cm focal length is placed 108.6cm
to the left of an eyepiece lens of +4.0cm focal length. Your eye is located very close to, and
to the right of the eyepiece. You are viewing the planet Jupiter, a very, very distant object,
through the telescope.
(a) At what distance from the eyepiece and to which side of it is Jupiter’s final image,
produced by the eyepiece? Is this a real or a virtual image?
(b) Jupiter has a diameter of about 140, 000km and you are vieweing it from a distance of
about 780, 000, 000km. How large, in units of mm, is Jupiter’s final image produced
by the eyepiece?
(c) Find the angle subtended at the eye by Jupiter’s final image, as seen through the
eyepiece! From that and from the appropriate reference angle, calculate the angular
magnification achieved with this telescope!
c 2015 University of Georgia.
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