JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
CHAPTER 6: WAVE
6.1 Understanding Waves
1. Motion of Waves
A wave front is a line or plane on which the vibration of every points on it are in phase
same
and are at the………….(same/different)
position from the source of the water.
circular
2. When we use a fingertip to touch the surface of water repeatedly, ……....(circular/plane)
wavefronts are produced.
3. Types of waves
There are 2 types of waves :wave Longitudinal
(a) Transverse
……………….
(b) wave
……………….
4. Transverse wave
(i). Transverse wave is a wave in which the vibration of particles in the medium is
perpendicular
at ……………….. (parallel/perpendicular) to the direction of propagation of the wave.
A
A
B
B
crest
A = … ……………….(crest / compression)
trough
B = …………………..(rarefaction /trough)
(ii). Example of transverse wave:
Water wave
i. ……………………………………..
Light wave
ii……………………………………...
Electromagnetic wave
iii……………………………………..
5. Longitudinal waves
(i) A longitudinal is a wave in which the vibration of particles in the medium is
parallel
……………………….(parallel
/ proportional) to the direction of propagation
P
of wave.
P
Q
Q
sound wave
(ii) Example of longitudinal wave:…………………………..
compression
P = …………………..(crest
/ compression)
rarefaction
Q = …………………..(rarefaction / trough)
1
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Amplitude, Period and Frequency of a Wave
A
C
A
B
B
C
Figure 6.20
1. Equilibrium position
2.
the position of the object where is no resultant force acts on the object.
is …………………………………………………………….
One complete oscillation of the pendulum occurs when the pendulum bob moves from
A-B-C-B-A
…………............
the time taken to complete an oscillation
3. The period, T of a vibrating system is ……………………………………………...
the number of complete oscillations
4. Frequency, f is ……………………………………………………
Hertz (Hz)
The S.I. unit is ……………..
1
n
f =
or
f =
T
t
5.
freeze waves patterns on the screen
Stroboscope is use to ……………………………………..
Stroboscope frequency = number of slits x rotation frequency of stroboscope
f = np
or
6. Wave speed
If the wavelength of the wave is λ , the waves move forward a distance of f x λ
per second. Therefore, the speed of waves, v
v=f λ
Question 3
In an experiment , Lim observes that a simple
Question
pendulum 2completes 30 ascillations in 48.0
A child on
a swing
swings in
seconds.
What
is makes 20 complete
2
30 seconds.
is the frequency of the
the
period ofWhat
oscillation?
oscillation?
The
frequency of oscillation?
Frequency, f
The number of complete oscillations per
second.
The S.I. unit is Hertz (Hz)
The number off complete
= 1
oscillations
or
f = per
n
second.
T
t
The S.I. unit is Hertz (Hz)
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
0
0
Exercise 6.1
Figure 6.10
A
1. (a) The wavelength of the wave in the diagram above is given by letter ……….
D
(b) The amplitude of the wave in the diagram above is given by letter …………
2. Indicate the interval which represents one full wavelength.
Figure 6.11
CG, BF,
Answer:AE,
……………………
3
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Exercise 6.11
1.
In an experiment , Lim observes that a simple pendulum completes 30 oscillations in
15.0 seconds. What is
(a) the frequency of oscillation?
(b) the period of oscillation?
Answer:
(a)
f = 30/15 = 2 Hz
(b) T = 1/f
= 1/2
= 0.5 s
Displacement/cm
2.
5
0
4
2
6
Time/s
-5
Calculate the frequency of the given wave above.
Answer : T = 4s
1
f=
Hz
T
= 0.25 Hz
Displacement/cm
5
0
-5
3.
2
4
6
Distance/cm
Based in the displacement-distance graph of a wave, find
(a) the amplitude
(b) the wavelength of the wave
Answer:
(a) amplitude = 5 cm
(b) Wavelength = 4 cm
4
JPN Pahang
Teacher’s Guide
4.
Physics Module Form 5
Chapter 6:Wave
A transverse wave is found to have a displacement of 4 cm from a trough to a crest, a
frequency of 12 Hz, and a distance of 5 cm from a crest to the nearest trough. Determine
the amplitude, period, wavelength and speed of such a wave.
Answer:
Amplitude: 4/2 = 2 cm
Wavelength: 5 x2 = 10 cm
Speed: v= f x λ = 120 cm s-1
5.
A girl moves a long slinky spring at a frequency of 3 Hz to produce a transverse wave
with a wavelength of 0.5 m. What is the wave speed of the waves along the slinky
spring?
Answer:
v=fxλ
= 3 x 0.5
= 1.5 m s-1
6.0 cm
•
6.
The figure shows a wavefront pattern in a ripple tank produced by a vibrating dipper at
frequency of 5 Hz. What is the wave speed?
Answer:
f = 5 Hz
λ = 6.0/4 = 1.5 cm
V=fλ
= 7.5 cm s-1
5
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
•
4.5 cm
7. The figure shows a wavefront pattern in a ripple tank produced by a vibrating dipper at
frequency of 5 Hz. What is the wave speed?
Answer:
f = 5 Hz
λ = 4.5/3 = 1.5 cm
V=f λ
= 7.5 cm s-1
20 cm (5λ)
8. A mechanical stroboscope has 12 slits and rotates at a frequency 5 Hz. The stroboscope
is used to observe water waves. The observer notes there are 6 successive bright bands at a
distance 20 cm. Calculate the speed of the water waves.
Answer:
f=np
= 12 x 5
= 60 Hz
9.
λ = 20/5
= 4 cm
V=fλ
= 60 x 4
= 240 cm s-1
The figure shows a loudspeaker produces a sound with a frequency 300 Hz. Calculate
(a) the wavelength.
(b) the speed of sound
Answer:
(a) 0.6 m
(b) V = f λ
= 300 x 0.6
6
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
= 180 m s-1
10. A given wave travels at a speed of 2 x 105 ms-1. If the frequency of the wave is 1000 Hz,
Calculate the wavelength
Answer:
λ= v/f
2 x10 5
=
= 200 m
1000
11. (a) Base on the figure determine,
(i)
the amplitude
(ii) the wave length
(b) What is the frequency of the sound if the speed of sound is 330 ms-1.
Answer:
(a) (i) 2 cm
(ii) 50 cm
(b) f = v / λ
= 330 / 0.5
= 660 Hz
Damping
Figure 6.12
7
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
1.
process whereby oscillations die down due to a loss of energy to friction forces.
Damping is a …………………………………………………………………………..
2.
decreases
When a system is damped , the amplitude of the of oscillation …………….
(decreases/increases) slowly until the system stops oscillating.
3.
Damping is usually caused by :(i) external frictional forces such as air resistance
(ii) internal forces , where energy is lost from the system in form of heat.
Resonans
phenomenon when the oscilating system is driven at its natural frequency by
A resonance isthe
……………………………………………………
a
periodic
force.
……………………………………………………………………………..
Experiment to show a phenomenon of resonance
E
A
B
D
C
Figure 6.12: Barton’s pendulum
Pendulum B and D are the same length. When pendulum B oscilates, all the pendulum start
to oscilate. But pendulum B and D have the same
length, so there have same natural
maximum
frequency. So pendulum D will oscilates with ……………(maximum/minimum) amplitude.
6.2
ANALYSING REFRLECTION OF WAVES
1.
Reflection of a wave occurs when a wave strikes an obstacle such as barrier, plane
reflector, mirror and wall.
2.
The
reflection
of incidence
waves obeys
the law
of reflection
:
(i) The
angle of
is equal
to the
angle of reflection.
………………………………………………………………
(ii)The incident wave, the reflected wave and the normal line in the same plane.
………………………………………………………………..
3.
When the reflection of a wave happened , the wavelength ,λ, the frequency, f and the
do not change
speed, v …………………….but
the direction of propagation of the wave changes.
8
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Exercise 6.2
Complete the diagram below.
Reflection of water waves
1. Show the pattern of the reflection of the water waves
(a)
(b)
(b)
2. Show the dark and bright pattern on the screen below.
9
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Water waves
Ripple tank
B
D
B
D
B
D
Screen
B
B = Bright
D = Dark
10
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Reflection of Light Wave
1. When rays of light strike any surface the rays are reflected , unless the surface is
black, when they are absorbed.
2. A plane mirror is a flat smooth surface which reflects regularly most of the light
falling on it.
Figure 6.20
1. The characteristics of reflection of light waves:
(i)
The size of the image = the size of the object
…………………………………………………………………
(ii) The distance of the image = the distance of the object
2. The bright and dark bands of the wave pattern formed on the screen because the
convex lens
surface of water acts as lenses. The crest of water waves similar with …………….
concave lens
(concave lens /convex lens) and the trough of water waves similar with ……
(concave lens /convex lens).
Exercise 6.21
The diagram shows a single ray of light being directed at a plane mirror. What are the
angles of incidence and reflection?
(a)
(b)
35o
Answer:
i =r = 90 – 55 = 35o
i = r = 70 o
2.
11
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Reflection of sound waves
1.
The sound waves is reflected by walls and ceilings of buildings, unborn baby or sea
bed.
Figure 6.21
2. The sound wave from the stopwatch experience a reflection after striking the smooth
wall.
equal to
The angle of incidence, i is ………….(equal to /more than/less than) the angle of
reflection, r.
Exercise 6.22
1.
The diagram shows a student shouting in front of a school building. Calculate the time
taken by the student to hear the echo of his voice.
[The speed of sound in air is 340 m s-1 ]
Answer:
2s = v x t
,
t=
2.
12
2(50)
340
= 0.29 s
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
If an echo is heard one second after the holler and reflects off canyon walls which are a
distance of 170 meters away, then what is the speed of the wave?
Answer:
2s = v x t
6.3
= 2 (170)
1
= 340 m s-1
ANALYSING REFRACTION OF WAVES
change of direction of the propagation of waves
1. The refraction of water waves occur when there is a ………………………………………
traveling from a medium to another medium due
to a change of speed.
Figure 6.30
1.
frequency
After refraction, the wave has the same …………………………. but a different
speed,
wavelength and direction.
………………………….
13
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Refraction of Water Waves
Deep
shallow
Figure 6.31
towards
1. When the water wave travel from a deep area, the direction of the waves is refracted ………
(towards/away from) the normal.
2. The angle of incidence, i of the water isgreater
………. (greater / smaller) than the angle of
refraction, r
3. When the refraction of a wave happened , the frequency, f does not change but the
wavelength
,λ, the
speed and the direction of propagation
………………
................................................................................of
the wave change.
Exercise 6.3
On each of the following diagram, draw the refracted wave by the perspex.
(a)
(b)
(c)
(d)
(e)
(f)
Refraction of water wave of the sea water
14
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Figure 6.32
1. Why are the speed and wavelength of waves in the middle of the sea almost uniform?
The depth of water in the middle of the sea is almost uniform.
………………………………………………………………………………………
2. What do you think would happen to the wave speed if the depth of water is increased?
The
speed increase
…………………………..
iniincreaseincreasedecre
.
3. Why do the distances between the wavefronts decrease as the waves approach the beach?
On approaching the beach, the depth of water decreases. The speed of waves decrese and the
……………………………………………………………………………………………
wavelength
is decreased.
4.
Why is the water in the bay stationary compared to the water at the cape?
The depth of water varies across the area of the bay
……………………………………………………………………………………………
The
energy of the water wave spreads to a wider area as compared to the region near the cape
The amplitude of the water wave near the bay is low and hence the water at the bay is
comparatively still
15
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Refraction of Light Waves
normal
air
glass block
Figure 6.33
1. When a ray propagates from one medium to an optically denser medium, the ray refracts
towards
…………………(towards
/ away from) the normal.
decreases
2. The speed of light …………….(decreases/increases) as it propagates in the glass block,
causing it to alter the direction of propagation.
Refraction of Sound Waves
Figure 6.34 (a)
Figure 6.34 (b)
1. Sound waves travel faster in warm air than incold
…….. (cold/hot) air.
2. On a hot day, the hot surface of the Earth causes the layer of air near the surface to be
warmer
………… (warmer/cooler)
3. This causes sound waves to be refracted
…………. (reflected/refracted) away from the Earth.
slower
4. On a cool night, the sound waves travel ………….(slower/faster)in the cooler layer of air
near the surface of the Earth than in the upper, warmer air. The waves are refracted
towards the Earth.
Hence, sound can be heard over a longer distance on a coldnight
……….(night/day) compared
with a hot day.
16
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
6.4 ANALYSING DIFFRACTION OF WAVES
the spreading out of waves when
1. Diffraction of waves is they
……..........................................................................
move through a gap or around an obstacle.
2. The effect of diffraction is obvious only if
small
(a) the size of the aperture or obstacle is …………..small / large enough.
large
(b) the wavelength is ……………… small /large enough.
speed
3. Frequency, wavelength and …………………of waves do not change
of propagation and the pattern of the waves are change
4. Thedirection
………………………………………….
Exercise 6.4
Complete the diagrams below by drawing the wavefronts to show the diffraction of water waves.
(a) Narrow gap ≤ λ
(b) Wider gap > λ
(c)Wider obstacle
From the diagram above,
(d) Narrow obstacle
1. Thenarrower
………….(narrower/wider) the gap, the more the waves spread out.
little
2. When the gap is much wider than the wavelength of the waves, there is ………….
(little/more) diffraction.
17
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Diffraction of light waves
Figure 6.40 Difraction of light through a single slit
Bright at the centre
Figure 6.41 (a)
Narrow slit
Figure 6.1(b)
Wide slit
1. The diffraction of light waves occur when the light waves pass through a small slit or
small pin hole.
2. The wider middle bright fringe shows that the light waves diffracted after pass
through a narrow slit.
less
3. If the slit becomes wider, diffraction pattern becomes ………….. (less/more) distint.
Diffraction of sound waves
Figure 6.42
A listener is requested to stand on the other side of the corner of the wall so that the radio
is beyond his vision.
2. The listener is able to hear the sound of the radio although it is behind the wall.
3. It is because the sound of the radio spreads around the corner of the wall due to diffraction
of sound.
1.
18
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
6.5 ANALYSING INTERFERENCE WAVE
1. Interference is the superposition of two waves from two coherent sources meet
amplitude
frequency
2. Two waves are in coherent if they are of the same ………………….and
………………,
3. There are two types of interference :
(a) Constructive interference
(b) Desctructive interference
Principle of superposition
When two waves overlap, the resultant displacement is
1. The principle of superposition states that………………………………………………………
equal to the sum of the displacements of the individual wave
…………………………………………………………………………………………………
the crests or troughs of both waves coincide to produce
2. Constructive interference occurs when…………………………………………………
a wave with maximum amplitude.
3.
the crests of one wave coincide with the trough of
Destructive interference occurs when………………………………………………………
the other waves to produce a wave with zero amplitude
4. (a)
Constructive Interference
+
=
Before superposition
During superposition
Figure 6.50 (a)
+
=
Before superposition
During superposition
Figure 6.50 (b)
19
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
When the vertical displacemet of two waves are in the same direction as in Figure 6.50
constructive
(a) and (b), …………………………(constructive/destructive) interference occurs.
(b)
Destructive Interference
+
=
Before superposition
During superposition
Figure 6.51
If a wave with a positive displacement meets another with a negative displacement of
the same magnitude, they cancel each other and the combined amplitude becomes
zero.
……….
Inteference of Water Waves
Figure 6.52: Inteference of water waves
1.
2.
At the points of constructive interference, the water moves up and down with a ………
large
…(large/ small) amplitude
antinodes
The points of constructive interferences, is known as …………..( nodes/antinodes)
nodes
The points of destructive interferences is known as ………………(nodes/antinodes).
20
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Exercise 6.5
B
C
A
Figure 6.53
1.
Figure 6.53 shows the interference pattern of water by two coherent sources of water
waves.
constructive
(i)
At point A, two crest meet resulting in ……………………….. interference.
constructive
(ii)
At point B, two through meet resulting in ……………………..interference.
destructive
(iii) At point C, a crest meet a trough resulting in …………………interference.
2.. Complete the table below.
Before superposition
During
superposition
2a
3a
21
After superposition
JPN Pahang
Teacher’s Guide
3.
Physics Module Form 5
Chapter 6:Wave
Categorize each labeled position as being a position where either constructive or
destructive interference occurs.
A,B
(a) Constructive interference:…………………….
C,D, E, F
(b) Destructive interference:……………………..
4.
.
The diagram shows a full-scale interference pattern of a ripple tank experiment 2
seconds after vibration started. The crests of the water ripples are repsented by the dark
lines.
(a) What is represented at P at this instant?
P is between two crest. Therefore, P represent a trough
………………………………………………………….
(b) What is the frequency of the vibrator?
The diagram shows crests from each source. In 2 seconds, 4 crests are produced.
…………………………………………………………
4
Thus the frequency is
= 2 Hz
2
5.
Two dot vibrators whoch has a separation of 5.0 cm are placed on a water surface in
a ripple tank. The distance between two adjacent antinodes on a screen is 3.0 cm. If
the perpendicular distance between the dot vibrators and the screen is 10.0 cm, what
is the wavelength of the water waves?
Answer:
5.0 x3.0
λ=
10.0
= 1.5 cm
22
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Inteference of Light Waves
1.
Interference occur when at least two coherent light waves overlap or superpose
2. The superposition of 2 rays produces:
constructive interference
(i) ………………………………………
destructive interference.
(ii)………………………………………
bright
3. When constructive occurs there will be a ………… (bright/dark) fringe
dark
When destructive occurs there will be a …………(bright/dark) fringe
4. The wavelength of monochromatic light can be found by the formula:
is the distance between the slits
a = …………………………………………………..
is the distance between consecutive bright or dark fringes
x = ………………………………………………….
is the distance between the double-slit and the screen
D = ………………………………………………….
23
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Exercise 6.51
1.
In a Young’s double slit experiment, a light of wavelength 633 nm passes through
two slit which are 0.5 mm apart. Vertical fringes are observed on a screen placed
4 m from the slits.
(i)
Calculate the distance between two adjacent bright fringes.
(ii)
What will happen to the distance between two adjacent bright fringes if
a light of shorter wavelength is used?
Answer:
(a) λ = 633 nm = 633 x 10-9
a = 0.5 mm = 0.5 x 10-3 m
D =4m
x=
633 x10 −9 x 4
0.5 x10 −3
x = 5.064 mm
(b)
If λ is smaller, x will also be smaller. Therefore , the distance between two
adjacent bright fringes of light will smaller.
14 mm
2. The wavelength of light can be determined with a double-slit plate. The diagram
above shows the pattern of interference fringes obtained in a Young’s double-slit
experiment. The separation distance of the two slit is 0.20 mm and the distance
between the screen and the double-slit plate is 4.0 m.
Calculate the wavelength of the light used in the experiment.
Answer:
6x = 14 mm
x = 2 mm = 2 x 10-3 m
D = 3.0 m
a = 0.2 mm = 2 x 10-4 m
2 x10 −4 x 2 x10 −3
λ =
4
= 1 x 10-7 m
24
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Inteference of Sound Waves
The wavelength of sound wave can be found by the formula:
distance between two loudspeakers
a = …………………………………………………..
distance between two consecutive loud places
x = ………………………………………………….
perpendicular distance between the speakers and
D = ………………………………………………….
the loud
Exercise 6.52
1. Two loud speakers placed 2 m apart are connected to an audio signal generator that is
adjusted to produce sound waves of frequency 550 Hz. The detection of loud and soft
sounds as a person moves along a line is at 4.0 m from the loudspeakers.
Calculate the
(a) wavelength
(b) speed
of the sound waves.
Answer:
(a) a = 2 m
D = 4.0 m
2x1.2
X=
= 0.6 m
4 .0
(b) f = 550 Hz
V=fλ
= 550 x 0.6
= 330 m s-1
25
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
6.6 Analysing Sound Waves
1. Sound waves are longitudinal wavces which require a medium for its propagation.
amplitude
2. The loudness of the sound is depend to the …………………
frequency
3. The pitch of the sound is depend to the ……………………...
4.
a phenomenon when a sound wave has been reflected off a
Echo is ……………………………………………………………………
surface , and is heard after the original sound.
Application of Sound Waves
1. Ultrasonic waves with frequencies above 20 kHz cannot be heard by human ear.
2. The ultrasonic ruler is used to measure the distance between itself and a target.
3. The depth of sea water can be calculated using the formula :
2d = v x t
Exercise 6.60
1. In an expedition to determine the depth of a freshwater lake using an ultrasonic
ruler, a pulse of ultrasonic sound is generated and travels to the bottom of the
lake and reflected by it. The time taken by the pulse to travel to the bottom of the
lake and return to the ruler is 0.35 s. If the speed of sound in freshwater is 1482
m s-1, calculate the depth of the lake.
Answer:
v = 1482 m s-1, t = 0.35 s
2d=vxt
1482x0.35
d=
= 259.35 m
2
26
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
2. Fill in the blank.
Field
Medicine
Industry
6.7
Application
Sound waves of high energy are directed
to the kidney stones to destroy them in the
cavity of the kidney.
Sound waves of high energy are directed
to the metal to determine the stretch.
Analysing Electromagnetic Waves
perpendicular
The electric and magnetic field vibrate ………………..(perpendicular/parallel) to
each other and to the direction of propagation.
2. Properties of electromagnetic waves
(i) Transverse waves
in a vacuum
(ii)Do not require a medium to propagate and can travel
8
-1
The
waves
travel
at
the
speed
of
light,
c
=
3
x
10
ms
(iii)
(iv)Undergo the same waves phenomenon : reflection, refraction, diffraction and
interference.
2. Sources and applications of electromagnetic waves in daily life
1.
Type of em wave
Radio waves
λ = 10-1 - 105 m
Microwave
λ = 10-3 – 10-1 m
Infrared
λ = 10-6 – 10-3 m
Visible light
λ = 10-7 m
Ultraviolet
radiation
λ = 10-9 – 10-7 m
X-ray
λ = 10-11 – 10-9 m
Gamma rays
λ = 10-14 – 10-10
m
Source
Electrical oscillating
circuit
Application
(a) telecommunications
(b) broadcasting : tv and radio
transmission
Oscillating electrical
(a) satellite transmissions
charge in a microwave
(b) radar
transmitter
(c) cooking
(a) night vision
Hot bodies, the sun and (b) thermal imaging and physiotherapy
fires
(c) remote controls
(a) sight
The sun, hot objects, light (b) photosynthesis in plants
bulbs, fluorescent tubes (c) photography
(a) identification of counterfeit notes
Very hot objects, the sun, (b) production of vit-D
mercury vapor lamps
(c) Sentrilisation to destroy germs
(a) Radiotherapy
x-ray tubes
(b) Detection of cracks in building
structures
(a) Cancer treatment
Radioactive subtances
(b) Sterilisation of equipment
(c) Pest control in agriculture
27
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Exercise 6.70
1. The diagram below shows the pattern of spectrum electromagnetic. In the boxes
provided, write the names of the parts given .
Radiowave
microwave gamma ray x-ray visible ray infra-red ray ultraviolet ray
wavelength
Gamma
ray
X-ray
Ultra
Violet
Visible
light
infrared
microwave
frequency
2. Table 6.70 shows electromagnetic waves P, Q, R and S and their uses
Electromagnetic waves
P
Q
R
S
Uses
Remote control
Radar system
Photograph
Kill cancerous cells
Table 6.70
Identify P, Q, R and S
Answer:
P = Infra-red rays
Q = Microwaves
R = Visible light
S = Gamma rays
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radiowave
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Reinforcement Chapter 6
Part A : Objective Questions
1. Calculate the frequency of the given wave above
A.
B.
C.
D.
E.
8 Hz.
1/8 Hz
4 Hz.
¼ Hz
12 Hz
2. Which of the following is NOT a electromagnetic wave?
A. x-ray.
B. Gamma ray
C. water wave
D. microwave.
3. Which of the following cannot travel through vacuum?
A.
B.
C.
D.
4.
x-ray
gamma ray
sound wave
light wave.
Based on the given diagram above calculate the wavelength.
A.
B.
C.
D.
E.
4 cm
8 cm
10 cm
15 cm
20 cm
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JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
5. Wave length of given wave does NOT depend on.
A.
B.
C.
D.
6.
velocity.
Frequency
Amplitude
Period.
What is the phenomenon shown above?
A. reflection.
B. Refraction.
C. Interference.
7. A given wave travels at a speed of 4 x 105 ms-1. If the frequency of the wave is 1000 Hz,
calculate the wavelength
A.
B.
C.
D.
E.
100 m
200 m
300 m
400 m
500 m
8. Which of the following is a common characteristic of visible light, ultraviolet rays,
infrared rays, gamma rays and X-rays?
A.
B.
C.
D.
9.
Which of the following electromagnetic waves are arranged in the order of increasing
wavelength.
A.
B.
C.
10.
Influenced by magnetic field.
Possess the same frequency.
Possess the same wavelength.
Possess the same velocity in vacuum.
Visible light, X-rays. Radio waves. Infrared waves.
X-rays. Visible light. Infrared waves .Radio waves.
Radio waves, X-rays. Visible light. Infrared waves.
Which of the following waves cannot travel through vacuum?
Sound waves
B. X-rays
C. Radio waves
A.
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JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Part B: Structured Questions
Figure 1
1. Figure 1 shows the use of sonar equipment to measure the depth of the sea.
(a) Reflection
State the phenomenon of sound wave applied in sonar equipment.
……………….
[1 mark]
(b) Sound waves with frequency of 6.0 x 105 Hz are used to determine the depth of
the sea. [speed of sound in sea water = 1500 m s-1]
(i)
(ii)
What is the wavelength of the sound wave in sea water?
v
1500
λ=
=
= 2.5 x 10-3 m
f
6.0 x10 5
[2 marks]
If the time interval between the instant the sound wave is sent to the
instant the echo is received is 1.5 s, what is the depth of the sea
d=
vt
1500x1.5
=
= 1125 m
2
2
[2 marks]
2.
Figure 2
A ping pong ball is held with a string and placed near a loudspeaker as shown
in Figure 2
The loudspeaker emits a low frequency sound and the ping-pong ball seems to
vibrate to it.
(a) Explain how the sound from the loudspeaker produces vibration on the ping
pong ball.
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JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
The vibration of the loudspeaker moves the air molecules around it.
The sound wave produced by the loudspeaker transfers energy to the ping
pong ball and causes it to move
(b) What will happen to the vibration of the ping pong ball if the loudness emits
(i) a louder sound?
The ping pong ball vibrates with greater amplitude
(ii) a sound with a higher pitch?
The ping pong ball vibrates with higher frequency.
(c)
If the frequency of the sound is 50 Hz, calculate the wavelength of the sound
produced. [Assume the speed of the sound in air in 350 ms-1]
v
350
=
= 7m
f
50
Figure 3 shows two sets of ripple tanks used to study diffraction of waves.
λ=
2.
(a)
(i)
Figure 3.1
Figure 3.2
What is meant by the diffraction of waves.
Diffraction is the spreading out of waves when they move through a gap
or around an obstacle
(ii)
Which of the two sets will show a bigger effect of diffraction. Explain
your answer.
The set shown in Figure 4.1 will show a bigger effect of diffraction. This is
because the narrower the gap, the more the waves spread out.
(iii)
Redraw and complete Figure 3.1 and Figure 3.2 to show the between the
two diffraction patterns.
(iv)
State the characteristic to the diffracted waves in terms of waves in terms
of wavelength, frequency, speed and amplitude compared to the incident
waves.
(a) Wavelength remains unchanged
(b) Frequency remains unchanged
(c) Speed remains unchanged
(d) Amplitude becomes smaller compared to the incident waves
32
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
Part C: Essay
1. Figure 3.0 shows the arrangement of the apparatus for an experiment to study a wave
phenomenon.
Figure 3.0
Figure 3.1 shows the bright and dark bands of the waves pattern formed on the white
paper when plane waves passes through the narrow and wide gaps.
Narrow gap
Figure 3.1(a)
Wide gap
Figure 3.1(b)
(a) Name the wave phenomenon shown in figure 1.2.
Diffraction
(b) (i)
√
[1 mark]
Explain how the dark and light bands are formed on the white paper.
[4 marks]
Figure / Troughs
act as a concave
lens
√
Figure / Crests
act as a convex
lens
√
√
B
D
B
D
Figure / Every troughs will
diverge the light, dark fringes are
formed
B
D
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B
Figure / Every crests will
converge the light, bright
fringes are formed
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
(ii) Observe Figure 3.2(a) and (b). Compare the waves patterns and the wavelength of
the waves before and after they pass through the gaps.
Relate the size of the gaps, the waves patterns and the wavelengths to deduce a
relevant physics concept.
[5 marks]
a.
b.
c.
d.
e.
In figure 3.1(a), size of the wavelength is the same as size of the gap // In figure
3.1(b), size of the gap is wider than size of the wavelength
In figure 3.1(a) and figure 3.1(b), size of the wavelengths are the same before and
after they pass through the gaps.
The waves emerging from the narrow gap in figure 3.1(a) is circular wavefronts
The waves emerging from the wider gap is plane wavefronts
When a wave passes through a gap, the wave spreads.
The narrower the gap the greater the spreading of the wave
Figure 1.3 shows the seashore of a fishing village. During the rainy season, waves
are big. One year the waves eroded the seashore, caused the jetty to collapse and
damaged the fishermen’s boats.
(c)
Figure 3.3
To prevent similar damage in the future, the fishermen suggest building retaining walls
and relocating the jetty.
Make further suggestion of ways to help the fishermen solve their problems.
You should use your knowledge of reflection, refraction and diffraction of waves to
explain these suggestions, to include the following aspects.
(i)
the design and structure of the retaining wall,
(ii)
the location of the new jetty
(iii) the size or energy of the waves
[10 marks]
Answer:
1. Build slanting barrier to reduce speed of wave
2. Build the rough barrier to reduce reflection of the waves
3. Build the new jetty at the bay because the water is calm at the bay
4. Build the small opening surround the bay because diffraction happens at the opening
5. Build the barrier at the bay because the wave is spread according to the shape of the
bay
34
JPN Pahang
Teacher’s Guide
Physics Module Form 5
Chapter 6:Wave
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