The document discusses reflection, refraction, and diffraction of waves. It includes definitions and explanations of these wave phenomena. Experiments are described to observe the reflection of water waves in a ripple tank and the refraction of both water waves and sound waves. Questions are provided about the key characteristics and behaviors of waves during reflection, refraction, and diffraction.

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What is Reflection
of wave?
 Occurs when a wave strikes an obstacle.
 The wave undergoes a change in direction of propagation when it is
reflected.
 The value of frequency (f), wavelength (λ) and speed (v) remain the
same after reflection.
Incident wave : the wave before it strikes the obstacle
Reflected wave: the wave which has undergone a change in
direction of propagation after reflection.
i = angle of incident – the angle between the direction of
propagation of incident wave and the normal
r = angle of reflection – the angle between the direction of
propagation of reflected wave and the normal.
State the Law of Reflection:
The angle of incidence, i is equal
to the angle of reflection, r.
Activity 1: Reflection of plane water waves in a ripple tank
Aim: To observe the reflection of plane water waves in a ripple tank
Apparatus: Ripple tank, plane reflector, white paper, wooden bar, lamp, motor, power supply,
sponge and mechanical stroboscope.
Procedure 1. Set up a ripple tank.
2. Switch on the motor to set
the vibrating. Increase the
frequency of the waves by
increasing the voltage
power supply to the motor.
3. Observe the reflected wave
by using a stroboscope.
Draw a
diagram to
show
reflection of
waves.
6.2

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Conclusion What will be the direction of travel of the reflected waves when:
(a) the incident water waves travel perpendicular to the barrier?
(b) the incident water waves travel at an angle to the barrier?
Questions 1. What is the wavelength of the reflected water waves compare to the
wavelength of the incident water waves?
2. When the speed of the motor increases, what will happen to the separation
between adjacent bright lines or dark lines?
Activity 2: Reflection of sound waves
Aim To investigate the reflection of sound waves
Apparatus 2 cardboard tubes, stopwatch, a softboard, a wooden board with a smooth
surface and a protactor.
Procedure
 Place a stop watch at the end of a hollow tube.
 The tube is place at an angle to a reflecting
surface.
 Keep a softboard vertical on the table top.
 Place another hollow tube on the other side of
the softboard and hold it close to your ear.
 Adjust the angle of the second tube until a loud
ticking is heard.
Discussion
i (°) 20 30 40 50 60
r (°)
What is the purpose of the soft board?
How is the angle of incidence related to the angle of reflection?
Conclusion In the reflection of sound, the angle of incidence is ……………… to the angle of
reflection.

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What is
Refraction of
waves?
Refraction of waves is a change of direction in the propagation of waves from one
medium to another due to a change of speed.
The frequency of the waves is equal to the frequency of the source of vibration and
hence it remains unchanged. But the speed, wavelength and direction of propagation
change.
What happens
to frequency,
speed,
wavelength &
direction?
The relationship between v and λ of a water
wave in deep and shallow water:
v = fλ f is constant
v v is directly proportional to λ
2
2
1
1
tan

vv
tcons
v
f 
Use the
words,
‘increase’,
decrease’ or
‘unchanged’
Characteristics
Water waves
passes from
deep water to
shallow water
Characteristics
Water waves
passes from
shallow water to
deep water
Speed Speed
Wavelength Wavelength
Frequency Frequency
How does the
direction of
waves change
when:
Water passing from the deep region to
the shallow region, the water wave is
refracted toward the normal.
Water passing from the shallow region to the
deep region, the water wave is refracted
away from the normal.
How to draw
a diagram to
show the
refraction of
waves?
1. Draw a line to represent the direction of propagation of the
incident waves.
2. Draw the normal, N at the boundary between the two areas.
3. Draw the line to represent the direction of propagation of the
refracted waves
4. Draw the refracted wavefronts.
6.3

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Activity 2: Refraction of Water Waves
Use a ripple
tank
Draw a ray
diagram to
show
refraction of
waves.
Discussion
5. Compare the wavelength for the water wave in the deep region and the shallow region.
6. Compare the frequency of the water wave in the deep region and the shallow region.

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7. By using the answer in question 1 & 2, and formula v = fλ, compare the speed of the water waves in
the two regions.
8. How does the direction of waves change when passing from the deep region to the shallow region?
9. When waves pass from the deep region to the shallow region, how do the following properties of the
wave change?
(i) Direction:
(ii) Wavelength:
(iii) Speed:
Conclusion
Explain the refraction of water.
Exercise 1
1. A plane wave has a wavelength of 2 cm
and a velocity of 8 cm s
-1
as it moves over
the surface of shallow water. When the
plane wave moves into an area of greater
depth, its velocity becomes 12 cm s
-1
.
What is
(a) the wavelength
(b) the frequency of the wave in the area of
greater depth?
2. The diagram shows a plane water wave
moving from one area P to another area Q of
different depth.
If the speed of water wave in P is 18 cm s
-1
,
what is the speed of water wave in Q?

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Refraction of water waves of sea water
 When the water waves propagated from the sea
to the beach , the water waves follow the shape
of the beach.
 It is because the water waves propagate from
the _______water to the ___________ water. The
speed and wavelength ___________ as the
waves approach the beach and hence the water
wave is refracted __________ the normal.
 The water in the bay stationary compared to the
water at the cape. It is because the depth of
water varies slowly across the area of the bay
and the _______ of the water wave spreads to a wider area 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.
Refraction of Light Waves
1. When a ray propagates from an
optically less dense medium to an
optically denser medium, the ray
refracts ___________ the normal.
2. The speed of light ____________ as it
propagates in the glass block, causing
it to change the direction of
propagation.
Refraction of Sound Waves
Figure (a) Figure (b)
1. Sound waves travel faster in warm air than in _______ (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/cooler)
3. This causes sound waves to be ____________ away from the Earth.
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 cold
_________(night/day) compared with a hot day.

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What is diffraction of waves?
Diffraction of waves is a phenomenon in which waves spread out as they pass through a ______
or round a small ____________.
The waves bend and change direction near the edges of the gap.
Small gap – more obvious large gap – less obvious
The effect of diffraction is obvious if the shape of the diffracted waves more spread out or more
circular
Small barrier – more obvious Large barrier – less obvious
What are Characteristics of diffracted waves?
1. Frequency, wavelength and speed of waves do not
change.
2. Changes in the ___________ of propagation and the
pattern of the waves.
3. The ___________ of the diffraction wave decreases so its
energy decrease.
What are the factors that influence the effect of diffraction?
The effect of diffraction is obvious if:
1. the size of the gap or obstacle is small enough
2. the wavelength is large enough.
6.4

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Activity 5: Diffraction of water waves in a ripple tank
Aim To study the characteristics of the diffracted waves.
Apparatus Ripple tank, lamp, power pack, stroboscope
Procedure
 A ripple tank is filled with water and set up as
shown.
 Switch on the power pack.
 Use a barrier to block the incident straight
water waves. Observe the wave pattern
beyond the barrier.
 Send a straight water waves to pass through a
gap. Observe the pattern of diffracted waves
beyond the gap.
 Send straight water waves towards a small
gap. Observe the wave pattern beyond the
small gap.
Observation
(a) Wide gap
The waves are …………. only at the edges
after passing through the gap.
The effect of diffraction is ……………………
(b) Narrow gap
The waves are …………….and appear to
originated from the small gap.
The effect of diffraction is …………..
Straight water wave propagate towards an
obstacle.

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Questions
1. Is there any difference in the wavelengths of the incoming waves and the diffracted
waves?
2. What can you deduce about the frequencies if the waves come from the same source and
are propagated in equal depths of water?
3. Will diffraction affect the amplitude of the diffracted waves?
4. What is the relationship between the shape of the diffracted waves with the size of the
gap?
Conclusions
As the size of the gap or obstacle …………………, the effect of diffraction becomes obvious.
Diffraction of sound
 Sound diffracting around corners so allowing us to
hear others who are speaking to us from adjacent
rooms.
 We can hear the sound of a radio placed nearby a
corner of a wall but we cannot see the radio. Why?
 Sound waves are more easily diffracted in
comparison to light waves because the wavelength
of sound waves is much __________ than the
wavelength of light waves.
Diffraction of light
Light is diffracted if it passes through a narrow slit comparable in size to its wavelength.
However, the effect is not obvious as the size of the slit increases. This is because the
wavelengths of light are very short.

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OBJECTIVE QUESTIONS
1 Which diagram shows the correct pattern of
reflected water waves? (2004)
2 Which of the following characteristics of
waves, changes when the waves are reflected?
(2007)
A. Direction of propagation
B. Wavelength
C. Frequency
D. Speed
3 Which of the following shows the effect of a
wave when a water wave is moving from a deep
region to a shallow region?
Speed Wavelength Frequency
A increases Increases Decreases
B Constant Decreases Increases
C Decreases Decreases Constant
D Increases Increases constant
4 When a light ray from air enters a glass, the
light ray is refracted into the glass. Which of
the following quantities remains constant when
the light ray is refracted into the glass?
A. speed
B. wavelength
C. frequency
D. intensity
5 The diagram shows a water waves propagate
from region P to region Q in a ripple tank.
Which statements explains the changing of the
direction of the water waves?
A. The water density in region P is higher
than in region Q.
B. Region P is deeper than region Q
C. Speed of water in region Q is larger
than region P
D. Amplitude of the water waves in region
Q is higher than region P
6 The diagram shows a refraction of a water
wave.
If the speed of the water wave is 5 cms
-1
in the
region of deep water, calculate the speed of the
water wave in the region of shallow water.
A. 1.5 cms
-1
B. 2.5 cms
-1
C. 3.0 cms
-1
D. 5.0 cms
-1
E. 5.2 cms
-1
7 A series of plane waves is produced in a ripple
tank containing a uniform depth of water. The
wavelength of a water wave changes when the
frequency of the wave changes. Which of the
following graphs shows the correct
relationship between the wavelength and
frequency of the wave?

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8 A ripple tank is not leveled so the depth of
water in the tank is not uniform. Water at X is
deeper than Y.
If the straight dipper vibrates to produce plane
waves, which diagram shows the correct path
of the wave when it reaches P?
9 The diagram shows water waves approaching
an island in the South China Sea.
What happens to the water waves after passing
the island?
Velocity Wavelength amplitude
A Increases Decrease No change
B Decreases Increases Increases
C No change No change Decreases
D No change No change No change
10 Which of the diagram below shows the of water
waves which passes through a small gap
correctly?
11
The diagram shows the pattern of water
approaching a shoreline. Which is the most
suitable locations for a child to swim?
12. Diagram 3 shows a ripple tank with a sloping
base and a vibrator being vibrated.
Which of the following wave patterns can be
seen on the screen? (2006)
13. A tilted basin contains water. Water is
dripped at a constant rate into the basin as
shown in the diagram below.
Which pattern of the wavefronts will be
observed in the basin? (2005)

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14. The diagram shows the wavefronts of a
plane wave incident on a plane reflector.
Which statement is correct about the
reflected and incident waves? (2005)
A. The speed of the reflected waves is the
same as the speed of the incident waves
B. The wavelength of the reflected waves is
shorter than that of the incident waves
C. The frequency of the reflected waves is
lower than that of the incident waves
D. The directions of the reflected waves are
always at right angles to the incident
waves.
15. Diagram below shows water waves
propagating in an area of different depths.
Which of the following diagrams shows the
propagation of the waves correctly? (2007)
STRUCTURE QUESTIONS
1. Figure 1 shows a water waves being
generated by a plane dipper oscillating in a
ripple tank with a deep area and a shallow
area.
Figure 1
(a) State two changes when the wave enters the
shallow area.
(b) If the frequency of the oscillating plane
dipper is 5 Hz, the wavelength of the waves
in the deep area is 4.0 cm and the
wavelength of the waves is the shallow area
is 3.0 cm, calculate:
(ii) the speed of the waves in the deep
area.
(iii) The speed of the waves in the shallow
area.
2. The figure shows successive wavefronts of
waves traveling on the surface of water a
ripple tank.
A perspex plat is placed on the bottom of a
ripple tank .

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(a) By drawing a straight line on the figure
above mark the boundary of the
perspex plat.
(b)(i)Determine the wavelength of the
waves before travels over the
perspex plat.
(ii) Calculate the frequency of the waves
before travels over the perspex plat
when the velocity is 40 cms
-1
.
(iii) Determine the velocity of the waves
travels over the perspex plat.
3. Figure 1 shows a water waves in a ripple
tank travels over a perspex plat.
Figure 2 shows a water waves propagated
from the sea to the beach.
Figure 1 Figure 2
(a) Based on Figure 1 and Figure 2
(i) state the change in wavelength of
the water waves from A to B.
___________________________
___________________________
(ii) compare the depth of water
between A and B.
___________________________
(iii) name a physical quantity is
unchanged .
___________________________
(b) Relate your answer in (a)(i) and (a)(ii) to
deduce a wave phenomenon.
(c) Name the phenomenon in (b)
________________________________
(d) The water waves with a wavelength of
1.5 m travels with velocity 2.0 ms
-1
from the sea to the beach. The velocity
of the waves when reach near the
beach is 1.2 ms
-1
.Calculate
(i) the frequency of the waves
(ii) the wavelength of the waves near
the beach
4. Figure 3 shows a tank with three areas of
water with different depths. A dipper
produces water waves in region Z and is
moving to region Y and X. Draw a diagram to
show how the waves propagate through the
three different area.

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5. The diagram shows water waves passing
through the entrance of a model harbour.
(a) Draw the pattern of the waves after
passing through the opening between
the walls.
(b) Name the wave phenomena shown in
the diagram.
______________________________
(c) Compare the size of the water wave
before and after passing through the
gap?
______________________________
______________________________
(d) By relating the size of the water wave
with the energy of the wave, explain
how does the wall protect the port from
being hit by large waves.
______________________________
______________________________
______________________________
6. Figures 6.1 and 6.2 shows plane waves
produced by linear dipper oscillating in a
ripple tank passing through gaps formed by
two straight barriers. Figure 6.1 shows
waves passing through a wide gap and
Figure 6.2 shows waves passing through a
narrow gap.
Figure 6.1
Figure 6.2
(a) (i) State a formula relating the speed, v,
wavelength, λ and frequency of a wave, f.
(ii) Using Figures 6.1 and 6.2, compare the
wave patterns and the wavelength of the
waves before and after they pass through
the gaps. Relate the size of the gaps, the
wave patterns and the wavelength to
deduce a relevant physics concept.
(iii)Name the wave phenomena shown in
Figure 6.1.
7. The figure below shows water waves
propagated from the sea towards the shore.
Observed the wave pattern and the sea-bed.
Based on the observations:
(a) State one suitable inference that can be
made.
(b) State one appropriate hypothesis for an
investigation.
(c) With the use of apparatus such as
ripple tank and other apparatus,
describe an experimental framework to
test your hypothesis.
In your description, state clearly the
following:
(i) Aim of the experiment
(ii) Variables in the experiment
(iii) List of apparatus and materials
(iv) Arrangement of the apparatus
(v) The procedure of the experiment
which include the method of
controlling the manipulated
variable and the method of
measuring the responding variable
(vi) Way you would tabulate the data
(vii) Way you would analysis the data
(SPM 2003)