Question

(i) If the angle of incidence and angle of emergence of a light ray falling on a glass slab are i and e respectively, prove that, i = e.

Answer 1

In the fig SR || PQ and OM is the reflected ray Hence r₁=r₂

Let μ be the refractive index of the glass slab.

Then, according to Snell's law,

Then, according to Snell's law,

$\frac{sini}{sin{r}_1}$ = μ .....(i)

and

$\frac{sin{r}_2}{sine}$ = $\frac{1}{\mu }$ .... .....(ii)

But r₁=r₂

Putting (iii) in (i), we get

$\frac{sini}{sin{r}_2}$ = μ .....(iv)

Multiplying (ii) and (iv), we have

$\frac{sini}{sin{r}_2}$ x $\frac{sin{r}_2}{sine}$ = μ x $\frac{1}{\mu }$

∴ $\frac{sini}{sine}$ = 1

∴ i = e proved