# Un polarised light passes through a polariser and analyser which are at an angle of 45° with respect to each other…..

Q. Un polarised light passes through a polariser and analyser which are at an angle of 45° with respect to each other. The intensity of polarised light coming from analyser is 5W/m². The intensity of unpolarised light incident on polariser is

(a) 5√3 W/m²

(b) 10W/m²

(c) 20W/m²

(d) 5 √3/4 W/m²

Ans: C

Sol: According to Malus Law

I2 = I1cos2 θ

I2 = I1cos2 45°

$\displaystyle I_2 = \frac{I_0}{2}cos^2 45$

$\displaystyle 5 = \frac{I_0}{2}\times \frac{1}{2}$

I0 = 20 W/m2