Explain reflection and refraction of waves.

(N/A) Reflection: When a wave reaches a boundary and the second medium is rigid,the wave is returned back into the first medium. This phenomenon is called reflection of the wave. Incident and reflected waves follow the law of reflection (angle of incidence equals angle of reflection).
Refraction: When a wave encounters an interface between two different elastic media,a part of the wave is reflected and a part is transmitted into the second medium. If the wave is incident obliquely on the boundary,the transmitted wave changes its direction. This phenomenon is called refraction of the wave. The incident and refracted waves obey Snell's law of refraction: $\frac{\sin i}{\sin r} = \frac{v_1}{v_2}$,where $v_1$ and $v_2$ are the wave speeds in the first and second media,respectively.