Question

Unpolarized beam of light of intensity I0 is incident on a polarizer P1. If another polarizer P2 is held parallel to it such that it’s pass axis is oriented at an angle of 60 degrees then what percentage of light will emerge from the system?

Answer 1

• Unpolarized light beam intensity = $I_{0}$; Need to find the % of light that will emerge from the system.
• Angle between the polarizers P1 and P2 = 60 deg
• Formula: I = $I_{0}$ $cos^{2}$$\theta$

• $cos^{2}$60 = $\frac{1}{4}$

• I = $\frac{I_{0}}{4}$
• From the output 25% of light is emerging from the system

Answer 2

Answer:

12.5%

Step-by-step explanation:

When the unpolarized light beam first enters the polarizer P1 the intensity I₀

becomes half.

Therefore,

I = I₀/2

Later when it passes through polarizer P2 kept an angle of 60⁰ w.r.t P1,

I' = (I₀/2)*cos²Ф

Therefore,

I' = (I₀/2) * cos²60

  = (I₀/2) * (1/2)²

  = (I₀/2) * (1/4)

  = (I₀/2) * 0.25

  = I₀ * 0.125

Converting to percentage,

⇒   I₀ * 0.125 * 100

I' = 12.5%