6.2.3 Refraction of Waves

Speed of Water Waves

1. When straight waves pass from deep to shallow water, their
   1. wave-length becomes shorter
   2. speed decreases
   3. frequency remain unchanged
2. This can be illustrated by placing a piece of rectangular Perspex of suitable thickness in the tank to reduce the local water depth.
   
3. Figure below shows the wavefront diagram of the wave formed.
   
4. We can see that the wavelength above the Perspex is shallower.
5. The relationship between the speed and wavelength of the wave in deep and shallow region is given by the formula below.
6. 
7. v_d = speed of wave in deep region
   λ_d = speed of wave in deep region
   
   
   v_s = speed of wave in deep region
   λ_s = speed of wave in deep region

Refraction of Waves at a Boundary

1. Refraction is the change in direction of propagation when a wave moves from one medium to another medium.
2. It is caused by the change of the speed of the wave when moving from one medium to another.
3. For water waves, refraction occurs when the waves move from one region to another region of different depth.
4. If water waves pass through a shallow region of convex shape, the waves will be converged.
   
5. If water waves pass through a shallow region of concave shape, the waves will be diverged.