Page 207 - text book form physics kssm 2020

Chapter 5
Waves
Example 2
P Q
Figure 5.43 shows propagation of water wave from
region P to region Q of diff erent depths. Speed of
–1
the wave is 18 cm s in region P. Determine the
speed of the wave in region Q.
Solution:

12 12 cm 12 cm
λ in region P, λ =
1 4
Figure 5.43
= 3 cm
12
λ in region Q, λ =
2 8
= 1.5 cm
Region P: λ = 3 cm, v = 18 cm s –1
1 1
Region Q: λ = 1.5 cm, v = ?
2 2
v v
1 = 2
λ λ
1 2
18 = v 2
3 1.5
18 × 1.5
v =
2 3
= 9 cm s –1

Formative Practice 5.4
5.4

1. What phenomenon of waves happens when sea waves are approaching the beach? Explain
your answer with the help of a diagram.

2. Figure 5.44 shows plane water waves of Deep region
frequency 10.0 Hz propagating from deep region P
to the boundary of shallow region PQ. Speed of λ
–1
the water wave in the deep region is 30 cm s . Shallow region
(a) Calculate the wavelength, λ.
(b) Calculate the speed of the water wave in
the shallow region if the wavelength in this Q
region is 1.5 cm. Figure 5.44
(c) Using arrows, draw the direction of propagation of the wave in the shallow region and
then sketch the wavefronts of water waves refracted in this region.
(d) Compare frequency, wavelength and speed in the deep and shallow regions.

201
5.4.4 201
5.4.4