Unpolarised light of intensity is allowed to fall normally on two identical Polaroid…

PHYSICS · Multi-part · A Level · Physics · Waves · Waves

Problem

Unpolarised light of intensity

I_0

is allowed to fall normally on two identical Polaroid sheets

P_1

and

P_2

placed one after the other. The transmission axis of

P_1

is fixed, while that of

P_2

can be rotated through any angle

\theta

with respect to the axis of

P_1

. (i) Show that the intensity of light emerging from

P_1

\dfrac{I_0}{2}

. (ii) Derive an expression for the intensity

I(\theta)

of the light emerging from

P_2

in terms of

I_0

and

\theta

. (iii) Find the value of

\theta

for which

I(\theta)

is (a) maximum and (b) one-fourth of

I_0

. (iv) Explain physically why no light emerges when

\theta = 90^{\circ}