Page 220 - text book form physics kssm 2020

In Activity 5.19, can you identify the constructive and destructive interferences for water,
light and sound waves?

Figure 5.60 shows the pattern of interference of water waves produced by two coherent sources
S and S in a ripple tank.
1 2

Line with interfaced bright and dark areas

S
1
Uniform grey coloured line
Bright
S + =
2 area Constructive
Dark + = interference
area
Grey + = Destructive
area interference

Figure 5.60 Interference pattern for water waves

INTEGRATION OF
HISTORY
Figure 5.61 shows the interference pattern formed on the screen
with light from a laser pen. Diff racted light waves that appear Activity on interference of
from the double-slit are coherent. Superposition of waves from light waves is also known
the double-slit produces a pattern made up of bright fringes and as Young’s double-slit
dark fringes. Constructive interference produces bright fringes experiment after the name of
while destructive interference produces dark fringes. a physicist, Thomas Young.
He successfully showed that
Bright fringe Dark fringe
light has wave characteristics
through experiments which
produce bright and
dark fringes.
Smaller distance of separation of slits Larger distance of separation of slits

Figure 5.61 Interference pattern for light waves
S
1
C.R.O. screen
Sound waves cannot be seen. Audio
Observer can only hear loud sounds signal
in constructive interference regions generator Key:
and soft sound in destructive Loud sound
interference regions. Figure 5.62 S 2 Soft sound
shows a waveform displayed on a
C.R.O. screen. Figure 5.62 Pattern of interference for sound waves

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5.6.1