Question

Unpolarized light of intensity Io passes through six successive Polaroid sheets each of whose axis makes a 60 ∘ angle with the previous one. What is the intensity of the transmitted beam?

Answer 1

Answer:

$0.00048828125I_0$

Explanation:

$I_0$ = Unpolarized light intensity

$\theta$ = Angle = 60°

Intensity of light through first polarizer

$I_1=\dfrac{I_0}{2}$

Intensity of light through nth polarizer

$I=I_1(cos^2\theta)^{n-1}$

when

n = 6

$I_6=\dfrac{I_0}{2}(cos^2(60))^{6-1}\\\Rightarrow I_6=0.00048828125I_0$

The intensity of light after passing through the sixth polarizer is $0.00048828125I_0$

Answer 2

Answer:

0.0004883 Io

Explanation:

Let Io be the intensity of unpolarised light.

Intensity of light coming out from first polaroid.

I1 = Io / 2

According to law of Malus, the intensity of light coming from the n th polaroid is given by

$I_{n}= I_{1}\left (Cos^{2}\theta  \right )^{n-1}$

where, n be the number of polaroid and θ be the angle between two polaroid.

$I_{6}= \frac{I_{0}}{2}\left (Cos^{2}60 \right )^{6-1}$

So, I6 = 0.0004883 Io

Thus, the intensity of light coming out from the sixth polaroid is 0.0004883 Io.