Unpolarized light from an incandescent lamp has an intensity 256.0 Cd as measure

Question

Unpolarized light from an incandescent lamp has an intensity 256.0 Cd as measured by a light meter.

a) What is in Cd the intensity reading on the meter when a single ideal polarizer is inserted between the bulb and the meter?

b) What is in Cd the intensity reading on the meter when two ideal polarizers are inserted between the bulb and the meter with their axis of polarization aligned?

c) What is in Cd the intensity reading on the meter when two ideal polarizers are inserted between the bulb and the meter with their axis of polarization making an angle of 45

Explanation / Answer

Single polarizer will reduce the intensity by 50%. Therefore once the polarizer is introduced intensity will be reduced to

I(one polarizer) = I0/2 = 256/2 = 128 Cd.

When the two polarizer with aligned axis are places the intensity remain 50%.

I(two polarizer with aligned axis) = 128 Cd

When the two polarizer make angle of 45 deg, intentity will be

I(two polarizer with 45 deg) = I0/2 cos2450 = 128/2 = 64 Cd

When the angle between the axis is 90 deg, the intensity will be 0 as cos90 = 0

I(two polarizer with axis 90 deg) = 0

When angle is 24 deg,

I(two polarizer with angle 24 deg) = I0/2 (cos240 )2 = 128 x 0.834 = 106.82 Cd

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