Saturday, January 1, 2011

REFRACTION OF WAVES

Definition :

Refraction of waves is a change in its direction as the waves pass from one medium to another.
It occurs when there is a difference in the speed of the wave at the boundary of two mediums.

What happens after refraction of wave?
The wave has the same frequency, but a different speed, wavelength and direction of propagation.

example :
1.Water waves passes from deep water to shallow water
The wave has the same frequency, but speed decrease, wavelength decrease and the the water wave is refracted toward the normal.

2. Water waves passes from shallow water to deep water
The wave has the same frequency, but speed increase, wavelength increase and the the water wave is refracted away from the normal.

Refraction phenomena :
1. A swimming pool seems much shallower than it actually is.
2. The sound of a moving car at a distance is clearer at night than that in the day time. This is due to the effects of the refraction of sound waves.

Relationship between frequency, speed and wavelength
.
v = f λ ( the wave frequency remain unchanged)
v ∝ λ
f 1 = f2

v1 = v2
λ 1 . λ 2

Quiz :
1.
A plane wave has a wavelength of 2 cm and a velocity of 8 cm s-1 as it moves over 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?