# find the value of angle of reflection

1 vote
402 views

Ordinary light incident on a glass slab at the polarizing angle suffers of deviation of 22 degree the value of angle of reflection ?

now what I thought is that when polarization take place the Brewster's law is valid and
$tan\theta_p=\mu$ where $\mu=$ refractive index of slab
and if its a glass slab so it would be 1.5

and since polarizing angle is same as angle of incidence then using brewster law it should come 56 degrees but that comes out to be wrong , then how to do this?

1 vote

There is no need to assume a value for refractive index. At the polarising angle of incidence $\theta_1$, the reflected and refracted rays are at right angles. Therefore
$\theta_1+90^{\circ}+\theta_2=180^{\circ}$
$\theta_1+\theta_2=90^{\circ}$.
We are told that the deviation is
$\theta_1-\theta_2=22^{\circ}$.
$2\theta_1=112^{\circ}$
$\theta_1=56^{\circ}$

One thing I couldn't understand why deviation$\theta_1 - \theta_2$. ?
Make a sketch, then you will see. $\theta_1$ is angle of incidence, $\theta_2$ is angle of refraction. $\theta_1 - \theta_2$ is angle of deviation.
No, $180-2i=180-112=68$. It should be $22$.