...

Physics 1252 Exam #1 Instructions:

by user

on
Category: Documents
1

views

Report

Comments

Transcript

Physics 1252 Exam #1 Instructions:
Physics 1252 Exam #1
Tue, 10 February 2015
Name:
Physics 1252
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 1252 Exam #1
Tue, 10 February 2015
Section
I
Score
/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. A light beam has a frequency of 300 GHz in a material of refractive index 1.5. When
the beam passes into a material with an index of refraction of 3.0, its frequency will be
A.
B.
C.
D.
E.
450
300
600
150
100
GHz.
GHz.
GHz.
GHz.
GHz.
2. UGA waves weren’t covered in class, but they do obey Snell’s law! They 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 always have an angle of refraction not exceeding 14.414o if the beam is
incident from above 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 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 smaller than the angle of incidence if the beam
is incident from below the interface without total internal reflection.
c 2015 University of Georgia.
Copyright 2
Physics 1252 Exam #1
Tue, 10 February 2015
Name:
3. Two identically shaped solid blocks, S, made from the same transparent material, are
immersed in two different liquids, L and M . 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 block, nS , and the liquids, nL and
nM ?
L
M
S
A.
B.
C.
D.
E.
S
nS < nM < nL ;
nM < nL < nS ;
nM < nS < nL ;
nS < nL < nM .
nL < nS < nM ;
4. A concave mirror M , a convergent lens L, and two small lightbulbs B and C, are
rigidly mounted in two empty tanks, as shown below. From B and C, M and L
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 the liquid benzene, compared to their
original locations in the empty tanks? (Hint: The index of refraction of benzene is
about 1.50 for visible light.)
L M B’ A.
B.
C.
D.
E.
B0
B0
B0
B0
B0
B C’ C moves towards or away from B; and C 0 does not move.
moves towards B; and C 0 moves towards C.
moves towards B; and C 0 moves away from C.
moves away from B; and C 0 moves towards C.
does not move; and C 0 moves towards or away from C.
c 2015 University of Georgia.
Copyright 3
Physics 1252 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 mirror, at distance from the
mirror which is greater than the absolute value of the mirror’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 mirror and its focal point, the object and the image, all of them clearly
labeled. Also clearly label the incoming and the outgoing side of the mirror. Is the image
real or virtual?
c 2015 University of Georgia.
Copyright 4
Physics 1252 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 = 1.60, through
the planar front surface, A, at an angle α, measured from A. The beam emerges from the
prism through the planar top surface B, at an angle β = 25o , measured from B, as shown
below. In parts (a) and (b), assume the prism is immersed in water, with nWater = 1.33.
(a) Find α!
(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 observed
angle β is 72o for α = 28o .
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.
Copyright 5
Physics 1252 Exam #1
Tue, 10 February 2015
Name:
IV: Galilean Telescope (35 points)
In a Galilean telescope, an objective lens of +110.0cm focal length is placed 106.6cm to the
left of an eyepiece lens of −3.0cm focal length. Your eye is located very close to, and to the
right of the eyepiece. You are viewing the planet Venus, a very, very distant object, through
the telescope.
(a) At what distance from the eyepiece and to which side of it is Venus’s final image,
produced by the eyepiece? Is this a real or a virtual image?
(b) Venus has a diameter of about 12, 100km and you are vieweing it from a distance of
about 150, 000, 000km. How large, in units of mm, is Venus’s final image produced by
the eyepiece?
(c) Find the angle subtended at the eye by Venus’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.
Copyright 6
Fly UP