(a)OR(b)

Identify electromagnetic waves which:

(i)

are used in radar system.

(ii)

affect a photographic plate.

(iii)

are used in surgery. Write their frequency range.

We consider, refracted wavefront CE and triangles ABC & AEC. From the triangles we obtained\sin \mathrm{i}=\frac{B C}{A C}=\frac{\mathrm{v}_{1} \tau}{A C} \sin \mathrm{r}=\frac{A E}{A C}=\frac{\mathrm{v}_{2} \tau}{A C}Thus $\displaystyle \frac{\sin i}{\sin r}=\frac{\mathbf{v}_{2}}{\mathbf{v}_{1}}$ We know $\displaystyle \mathrm{n}=\frac{c}{\mathrm{~V}}$, So $\displaystyle \frac{\sin \boldsymbol{i}}{\boldsymbol{\operatorname { s i n }} \boldsymbol{r}}=\frac{\boldsymbol{n}_{\mathbf{2}}}{\boldsymbol{n}_{\mathbf{1}}}$ which is the Snell's law.