UNIVERSITY OF ABUJA
DEPARTMENT OF PHYSICS
FIRST SEMESTER EXAMINATION 2020/2021 SESSION
PHY103: Introductory Optics, Waves and Sound (3 Units)
TIME: 3 hours
Answer ALL questions
Where appropriate the speed of light 𝑐 = 3.0 × 108 m/s
𝜋 = 3.142
1) Anything from which light rays radiate is called what?
(a) an image (b) a ray (c) an object (d) wave front
2) What is the wavelength range of visible light?
(a) 800-900 nm (b) 400-700 nm (c) 100-300 nm (d)10-90 nm
Use this figure to answer questions (3) to (8)
12) Reflection from any rough surface is known as what?
(a) directed reflection. (b) diffuse reflection. (c) perfect reflection.
(d) smooth reflection.
13) The use of geometry to understand how light rays form images is
known as?
(a) ray waves (b) geometric optics (c) electrodynamics (d)
electrolysis
14) When is a mirror said to be perfect?
(a) when it shines very brightly. (b) when it is very smooth. (c) when
it reflects 100% of the incoming light. (d) when it can allow the
passage of some light.
15) The deviation from straight-line propagation that occurs when a
wave passes beyond a partial obstruction is ___?
(a) diffraction (b) interference (c) refraction (d) reflection
16) A dental technician uses a small mirror that gives a magnification
of 4.0 when it is held 0.60 cm from a tooth. What is the radius of
curvature of the mirror?
(a) 2.6 cm (b) -1.6 cm (c) 1.6 cm (d) 2.0 cm
3) Which of the lenses is a diverging meniscus?
(a) F
(b) B
(c) C
(d) D
4) Which is a diverging lens?
(a) E
(b) B
(c) C
(d) D
17) The Eye uses a variable-focus lens to form an image on the _?
(a) retina (b) lens (c) pupil (d) iris
18) Which is not an example of an optical instrument
(a) camera (b) lamp (c) microscope (d) telescope
Use this figure to answer questions (19) to (23)
5) Which is a converging lens?
(a) A
(b) D
(c) F
(d) C
6) Which of the lenses is a converging meniscus
(a) A
(b) B
(c) C
(d) D
7) Which is a planar converging lens?
(a) D
(b) E
(c) B
(d) F
8) Which is a planar diverging lens?
(a) C
(b) D
(c) F
(d) E
9) In geometric optics, when is a surface referred to as smooth?
(a) If the surface is well polished. (b) if light can penetrate. (c) If its
variations are small compared with the wavelength of the incident
light. (d) If it allows light rays to be scattered unevenly
10) The law of reflection states that___?
(a) the angle of incidence is always larger than the angle of
reflection. (b) the angle of incidence is always less than the angle of
reflection. (c) light rays cannot enter a lens. (d) the angle of
incidence equals the angle of reflection.
11) What happens during reflection of rays at a boundary?
(a) the incident ray, reflected ray, and normal to the surface all lie in
the same plane. (b) the incident ray, reflected ray, and normal to the
surface all lie in different planes. (c) only the normal to the surface
and the reflected ray lie in the same plane. (d) only the reflected ray,
and normal to the surface all lie in different plane.
19) Which letter represent the optical axis of the mirror?
(a) A
(b) D
(c) B
(d) f
20) Which letter represent the image distance?
(a) A
(b) f
(c) B
(d) e
21) Which letter represent the image?
(a) A
(b) C
(c) B
(d) D
22) Which letter represent the object?
(a) D
(b) C
(c) B
(d) A
23) The figure describes image formation by what kind of mirror?
(a) concave (b) convex
(c) plane
(d) converging
24) Which is not a kind of mirror?
(a) concave (b) convex
(c) plane
(d) diffuse
25) The principle which states that we can consider every point of a
wave front as a source of secondary wavelets is __?
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(a) Huygens's principle (b) Maxwell's principle (c) Newton's
principle (d) Hilbert's principle
26) Compute the position of the converging thin lens, which will
project the image of a lamp, magnified 4 times, upon a screen 10.0
m from the lamp
(a) 1.6 m (b) 0.7 m (c) 1.2 m (d) -1.2 m
𝑠𝑖𝑛 𝜃2
𝑣2
27) The expression
=
can be described as who's
𝑠𝑖𝑛 𝜃1
𝑣1
law?
(a) Newton's law (b) Snell's law. (c) Faraday's law. (d) Maxwell's
law
28) Which of the following is a defect of lenses
(a) lack of a principal focus. (b) larger image size than the object. (c)
curvature imbalance. (d) spherical aberration
(a) D (b) E (c) A (d) C
36) What letter represent the reflected ray?
(a) D (b) E (c) A (d) C
37) What letter represent the refracted ray?
(a) D (b) E (c) A (d) C
38) What letter represent the incident ray?
(a) D (b) E (c) A (d) C
39) What is 𝜃2 ?
(a) angle of reflection (b) angle of incidence (c) refracted ray (d)
angle of refraction
40) If 𝜃2 < 𝜃1 which statement is correct?
(a) 𝑣2 > 𝑣1 (b) 𝑣2 = 𝑣1 (c) glass is denser than air (d) air is denser
29) In what two positions will a converging thin lens of focal length than glass.
+9.00 cm form images of a luminous object on a screen located 40.0
cm from the object?
41) Compute the position of the image of the Moon in a polished
(a) 7.3 cm and 1.7 cm (b) 12.3 cm and 9.7 cm (c) 7.7 cm and 18.7 sphere of diameter 20 cm. The diameter of the Moon is 3500 km,
cm (d) 13.7 and 26.3 cm.
and its distance from the Earth is 384 000 km, approximately.
(a) 5.0 cm (b) 2.5 cm (c) -5.0 cm (d) -2.5 cm
30) The relationship between the speed of light in a vacuum c and
𝑐
42) Compute the diameter of the image of the Moon in question
the speed of light in a particular material v is given by
= 𝑛.
number (41).
𝑣
What is n called?
(a) 5.0 nm (b) 0.46 nm (c) 0.89 nm (d) 2.5 nm
(a) velocity (b) refractive index (c) normal (d) normal setting
43) The atoms in an HCl molecule vibrate like two charged balls
31) One of the following is a condition for interference
attached to the ends of a spring. If the wavelength of the emitted
(a) waves must first be reflected. (b) waves must travel in opposite electromagnetic wave is 3.75 μm, what is the frequency of the
direction. (c) waves must travel in the same direction. (d) waves vibrations? [hint 𝑐 = 𝑓𝜆, 1μm = 10−6 m].
must have identical wavelengths.
(a) 1.38 × 1012 Hz (b) 1.8 × 1013 Hz (c) 8.0 × 1013 Hz (d)
3.2 × 1011 Hz.
32) A convex spherical mirror has a focal length of -1.00 m. A small
object is 2.00 m in front of the mirror on its central axis. Locate the 44) An observer on the west-facing beach of a large lake is watching
image.
the beginning of a sunset. The water is very smooth except for some
(a) -1.6 m (b) -0.67 m (c) 1.2 m (d) -1.2 m
areas with small ripples. The observer notices that some areas of the
water are blue and some are pink. Why does the water appear to be
33) Calculate the magnification of the object in question (32).
different colors in different areas?
(a) -1.8 (b) -0.67 (c) 0.33 (d) 0.67
(a) the different colors arise from multiple refraction. (b) the
different colors arise from diffraction. (c) the different colors arise
Use this figure to answer questions (34) to (40)
from specular and diffuse reflection. (d) the different colors arise
from multiple refraction and diffraction.
45) A typical compact disc stores information in tiny pits on the
disc’s surface. A typical pit size is 1.2 μm. What is the frequency of
electromagnetic waves that have a wavelength equal to the typical
CD pit size? [hint 𝑐 = 𝑓𝜆, 1𝜇m = 10−6 m].
(a) 2.48 × 1013 Hz (b) 3.5 × 1013 Hz (c) 2.5 × 1011 Hz (d)
2.5 × 1014 Hz.
34) What letter represent the normal?
(a) C (b) E (c) A (d) B
46) The Nigerian Army’s loudest loudspeaker is almost 2.0 m across.
The sound is produced by an electromagnetic coil that can generate
a minimum frequency of 5.0 Hz.What is the wavelength of these
electromagnetic waves?
(a) 6.0 × 107 m (b) 1.5 × 109 m (c) 3.0 × 109 m (d) 1.5 ×
107 m.
35) What letter represent the boundary?
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47) A human hair is about 80.0 𝜇m thick. If one uses a concave
mirror with a focal length of 2.50 cm and obtains an image of −59.0
cm, how far has the hair been placed from the mirror?
(a) 2.4 × 10−2 m (b) 2.0 × 102 m (c) 2.5 × 10−3 m (d) 8.5 ×
10−2 m.
where 331 m/s is the speed of sound in air at 0°C, and TC is the
temperature in degrees Celsius. What is the speed of sound at 25°C?
(a) 3.46 × 102 m/s (b) 3.31 × 102 m/s (c) 3.46 × 103 m/s (d)
3.31 × 103 m/s.
58) One of the options is not a factor that affect the speed of sound
in a medium.
(a) compressibility (b) wideness (c) inertia (d) density
48) What is the magnification of the hair in question (48)?
(a) 12.4 (b) 4.5 (c) 16.8 (d) 24.6
59) When light enters from vacuum in to glass, it's velocity
(a) decreases (b) remains same (c) increases (d) varies depending on
mass of glass
Use this figure to answer questions (49) to (52)
60) As wave travels, intensity
(a) decreases (b) remains same (c) increases (d) varies
61) Frequency and time period of a wave are
(a) directly related (b) not related (c) directly proportional (d)
inversely related
62) From double-slit experiment, the quantities to be measured are.
(a) slit separation (b) fringe separation (c) slit-to-screen distance (d)
all of above
49) What is the name given to points B and D?
(a) bottom (b) crests (c) troughs (d) tops
63) Constructive interference happens when two waves are
(a) zero amplitude (b) in front (c) in phase (d) out of phase
50) What is the name given to points A, C and E?
(a) troughs (b) crests (c) tops (d) axis
64) When two sound waves having nearly the same frequency
interfere, we hear variations in the loudness called
(a) waves (b) beats (c) interference (d) superposition
51) What is 𝑦0 ?
(a) wavelength (b) crests (c) troughs (d) amplitude
65) In young double slit experiment, the wavelength of incident
beams should be
(a) same (b) different (c) zero (d) opposite
52) What is λ?
(a) wavelength (b) amplitude (c) crest (d) trough
53) The faintest sounds the human ear can detect at a frequency of
1× 103 Hz which corresponds to an intensity of about____?
(a) 1.0 × 1012 W/m2 (b) 1.0 × 10−12 W/m2 (c) 1.0 × 102 W/
m2 (d) 1.0 × 10−2 W/m2 .
54) Waves that have the same form, the same frequency, and a fixed
phase difference are called _____?
(a) progressive waves (b) coherent waves (c) interference waves (d)
disruptive waves
55) When two or more waves overlap, the resultant displacement at
any point and at any instant is found by adding the instantaneous
displacements that would be produced at the point by the individual
waves if each were present alone. What principle is that?
(a) Newton's principle (b) Huygens's principle (c) Principle of
superposition (d) Principle of constructive interference.
56) One of the following is not a category that covers different
frequency ranges under which sound waves are divided.
(a) ultrasonic waves (b) infrasonic waves (c) infrared waves (d)
audible waves.
66) Interference pattern of light and dark bands on screen is called
(a) graphical pattern (b) fringes (c) light spectrum (d) line spectrum
67) Spreading of wave as it passes through a gap or around an edge
is called
(a) reflection (b) refraction (c) diffraction (d) superposition
68) When two waves meet, their displacements
(a) destruct each other (b) add up (c) cancel out (d) subtract down
69) Waves that moved in the same direction as the source is moving
are shortened, making the pitch of the sound higher. What effect is
this?
(a) Velocity effect (b) Breeze effect (c) Doppler effect (d)
Wavelength effect
70) What is the unit of sound level?
(a) luminosity (b) decibel (c) loudness (d) hertz
[Good Luck (~_~)]
57) For sound traveling through air, the relationship between wave
speed and medium temperature is 𝜈 = (331𝑚/𝑠) √1 +
𝑇𝑐
273𝑜 𝐶
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