Transcript PHY504 Midyear Practice Exam Questions

PHY504 Midyear Practice Exam Questions
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Please keep in mind that you will have 3 hours to complete the January
exam, and that it will have 15 questions based on everything we have
learned throughout the Geometric Optics unit.
There will also be a single question asking you to explain the optics
behind a device (similar to what you were asked to do for your
project). Background information will be provided about the device to
assist you.
Finally, please be sure that you have a geometry set as well as a nongraphing SCIENTIFIC calculator and writing implements for your
January exam (as none will be provided).
These sample questions are provided to help you focus your studies
and test yourself. Completing these practice questions is not sufficient
preparation for the exam!!
1. Which of the following light phenomena
accounts for the colours in a rainbow?
A) Diffraction
C) Dispersion
B) Diffusion
D) Reflection
2. The following diagram depicts a
side-view mirror of a car.
On the mirror is written:
Objects are closer than
they appear.
What type of mirror would produce this effect?
A) Plane
C) Converging
B) Convex
D) Concave
3. Julie came back from the ophthalmologist who told
her she is suffering from hyperopia, a condition in
which images are formed behind the retina in the eye.
3. Which one of the following correction lenses
would help Julie?
A) Plane
C) Convex-concave
B) Plano-concave
D) Concavo-convex
4. Haran is manipulating a concave mirror that has a focal
length of 10.0 cm. His physics teacher tells him that the
difference between do and di is 15.0 cm and that the image
is larger than the object and has a negative magnification.
Where should Haran place the object to obtain the
desired image?
A)
B)
C)
D)
do = 15.0 cm and di = 30.0 cm
do = 30.0 cm and di = 15.0 cm
do = 5.0 cm and di = -10.0 cm
do = 10.0 cm and di = -5.0 cm
4. A pinhole camera was set up
to view a 5.0 cm matchstick.
The distance to the matchstick was
twice the depth of the camera.
What was the height of the image
on the screen?
A)
B)
C)
D)
50.0 cm
10.0 cm
5.0 cm
2.5 cm
6. Which of the following explains why this
page (screen) is visible?
A)
B)
C)
D)
It
It
It
It
is incandescent.
emits light.
refracts light.
reflects light.
7. The four diagrams below show a single ray of light
reflected off surfaces of different shapes. All the
surfaces are covered with polished metal.
Which diagram does not respect the law of reflection?
A) Diagram 1
B) Diagram 2
C) Diagram 3
D) Diagram 4
8. Which illustrations correspond to each of the
phenomena listed below?
Write the letter of the illustration on the
corresponding numbered line of the phenomenon.
Phenomena
1. Specular reflection B
2. Diffuse reflection E
3. Refraction A C
A
B
C
D
E
9. The converging lens of a slide projector has a focal length
of 10.0 cm. This lens is located 4.10 m from a vertical
screen.
A slide is placed in the projector and the lens is adjusted to
produce a clear image on the screen. What is the distance
between the lens and the slide?
A)
B)
C)
D)
2.50
1.00
1.03
2.38




10-1 cm
101 cm
101 cm
101 cm
10. A lens system is made up of two lenses cemented
together. The focal lengths of these lenses are 50 cm
and -40 cm.
What is the optical power of this lens system?
A)
B)
C)
D)
-0.50 dioptre
0.10 dioptre
4.5 dioptres
10 dioptres
11. The following diagram shows a concave mirror. To
produce an upright image, where should the object be
placed?
A)
B)
Point A
Point B
C) Point C
D) Point D
12. A professional photographer uses umbrella-shaped
screens made of aluminum foil and a white screen set
up behind the object to be photographed.
What is the purpose of the umbrella-shaped screens?
A) They concentrate the light emitted
by the camera onto the object to be
photographed.
B) They reflect the light from the
projection lights onto the object so
that it is illuminated from all sides.
C) They obtain specular reflection of the
light emitted by the object.
D) They concentrate the reflected light on
the photographic equipment.
13. The sextant illustrated below has been set to view the
image of only one of the four stars shown in the diagram.
Which star can be
observed?
A) Star 1
B) Star 2
C) Star 3
D) Star 4
14. A person is walking towards a plane mirror at a
speed of 1 m/s. At the same time, the image of this
person formed by the mirror is also moving.
Which of the following statements is TRUE?
A) The image is approaching the
person at a speed of 2 m/s.
B) The image is approaching the
person at a speed of 1 m/s.
C) The image is moving from the
person at a speed of 2 m/s.
D) The image is moving from the
person at a speed of 1 m/s.
15. In a laboratory experiment, the following set up was established.
The obstacle was then moved closer to the screen, while the light
source remained in the same position.
How will the area of the penumbra
on the screen change?
A) The area of the penumbra on
the screen will decrease.
B) The area of the penumbra on
the screen will remain the same.
C) The area of the penumbra on
the screen will increase.
D) The area of the penumbra on
the screen will first increase then decrease.
16. The following diagram shows a light ray striking
a concave spherical mirror.
16. Which of the following diagrams best
represents the path of the light ray reflected by
the mirror?
A)
B)
C)
D)
17. Using three mirrors, a school bus driver is able to view students
leaving the bus. One plane mirror and two convex mirrors are shown in
the following diagram. There are 5 students surrounding the bus.
Symbols: 
Represents the driver’s eye.

Represents the students.
C
Represents the centre of curvature.
Construct field of vision diagram,
identifying the student(s) the driver
CANNOT see in the mirrors.
17.
18. During an experiment on optical power and lens
combinations, Sophie came up with a calculated optical
power of 0 dioptres for a set of two lenses. Hassan, her lab
partner, concluded that the result could not be possible.
Who is right?
How would you justify your answer from an optics point of view? Support
your answer, in a short written justification, using all three of the
following concepts:
 optical power
 focal length
 magnification
Optical power is additive so a negative and positive lens could be used to
cancel each other out (e.g. 2δ & -2δ). Focal length is not additive and
should not be used to determine the combined effect of two lenses. An
optical power of zero corresponds to an infinite focal length. See,
www.colorado.edu/physics/phys1230/phys1230_fa01/topic27.html
19. Nadia is conducting a physics experiment using a
converging lens on an optical bench. The professor has
said that the object must be 64.0 cm from the screen.
Nadia is told that the focal length of the lens is 12.0 cm
How far from the object must Nadia place the lens to obtain a clear and
larger image on the screen? Show all your work.
19.
F = 0.12 m
di + do = 0.64 m
do = ?
Potentially relevant equations.
19.
𝑑𝑜 𝑑 − 𝑑𝑜 = 𝑓 𝑑 − 𝑑𝑜 + 𝑑𝑜 = 𝑓𝑑
𝑑𝑜 2 − 0.64 𝑚 𝑑𝑜 + 0.64 𝑚 0.12 𝑚 = 0
𝑑𝑜 must be between f & 2f, Table 2, p. 114.
𝑑𝑜 = 0.16 𝑚
20. A glass prism with a refractive index of 1.5 is used with
a light source in the form of an arrow.
The light enters the perpendicular prism through the
nearest side.
Θc = arcsin( 1.0 / 1.5)
= 41.8°
45° is greater than Θc,
so there is total internal
reflection
Show the orientation of the arrow as the beam exits the
prism. Show all lines.
21. Optical fibers are now widely used in telecommunications.
Sound waves are transformed into light waves which are then
transmitted by optical fibers.
Which light phenomenon makes it possible to use optical
fibers for this purpose?
Total internal reflection is used so that the light will reflect
internally along the length of the optical fiber without losing
light via transmission through the walls of the fiber. The outer
surface of the fiber is coated with a material that has a lower
index of refraction than the core of the fiber.
22. The diagram on
Θi = 45°
the right represents a
box through which
Θi = 45°
light is to pass from
opening A to opening
Θi = 45°
B. Several small
plane mirrors are
available.
How would you place the mirrors in the box so that the
light passes from A to B?
On the diagram in the answer booklet, draw lines to
indicate the position of the mirrors and the path of the
rays; also specify the values of the angles of incidence. All
elements must be included for marks to be allotted.
23. The index of refraction for a certain kind of glass is 1.67
for blue light and 1.61 for red light. A beam containing
these two colours hits the glass with an angle of incidence
of 45°. (Diagram is not drawn to scale.)
Θi = 45°, nr = 1.61, Nb = 1.67
Calculate the angle between the two refracted rays.
24. Draw a diagram in the Answer Booklet to show
where an object must be placed in order for it to be
illuminated by the two rays I1 and I2. Draw the reflected
rays.
25. The diagram below represents an object and
a converging lens.
Knowing the focal point of the lens, state two
characteristics of the image formed by this system.
Since the focal point is in front of the lens, the lens is
diverging or negative lens. It will produce a real, inverted
image smaller than the object, p.114.
26. For each of the following diagrams, identify the
defect in the eye, if there is one, and indicate the kind of
lens needed to correct the defect and restore normal
vision.
Defect: ____________________
Hyperopia
Diagram 1
Type of Lens: ___________________________
Converging Lens
Diagram 2
Diagram 3
Defect: ____________________
Emmetropia
Type of Lens: ___________________________
None
Defect: ____________________
Myopia
Type of Lens: ___________________________
Diverging Lens
27. A 2.0 cm tall object is located 4.0 cm from a converging lens that has
a focal length of 12 cm.
What is the magnification of the image?
Potentially relevant equations.
Check Table 2, p. 114
28. A light ray travelling in air enters an unknown substance
at an angle of incidence of 40.0°. The angle of refraction is
25.4°. Determine the value of the critical angle for this
unknown substance. Show all your work.
40°
Θi = 40.0°
θR = 25.4°
n1 = 1
25.4° n2 = ?
𝑛1 sin θ𝑖
1 sin 40°
𝑛2 =
=
= 1.50
sin θ𝑅
sin 25.4°
Θc = arcsin( 1 / 1.50) = 41.8°
29. Illustrated below is the inside of a closed box. There is one hole through which
a light ray enters as shown.
nair = 1.0
nprism = 1.5
Where should a second hole be placed in order for the light
ray to exit the box?
You must show the complete path of the light ray to find your
answer. Show all your work.
29.
30°
30°
19.5° 70.5°
θ𝑡 =
sin−1
1 sin 30°
= 19.5°
1.5
nair = 1.0
nprism = 1.5
29.
nair = 1.0
nprism = 1.5
Θc = arcsin( 1 / 1.50) = 41.8°
70.5°
40.5°
49.5°
76.9°
θ𝑡 =
sin−1
1.5 sin 40.5°
= 76.9°
1
30. A candle, AB, is placed in front of a plane mirror. On the
diagram in your Answer Booklet, locate and draw the image
of the candle. Using the image of the candle, then draw light
rays that show how the eye sees point B on the candle in the
mirror.
Show all your work.