KVPY SX SB Exam 19-Nov-2017 Question Paper

Question : 24 of 120

Marks: +1, -0

Three circularly shaped linear polarisers are placed coaxially. The transmission axis of the first polariser is at 30°, the second one is at 60° and the third at 90° to the vertical all in the clockwise sense. Each polariser additionally absorbs 10% of the light. If a vertically polarised beam of light of intensity I = 100 W/m

^{2}

is incident on this assembly of polarisers, then the final intensity of the transmitted light will be close to

10 W/m $^{2}$
20 W/m $^{2}$
30 W/m $^{2}$
50 W/m $^{2}$

Validate

Solution:

I_1 = I_0 × 0.9 \cos^230°

= I_0 × 0.9 × 3/4

I_2 = I_1× 0.9 \cos^230°

= I_1 × 0.9 × 3/4

I_3 = I_2 × 0.9 \cos^230°

= I_2× 0.9 × 3/4

⇒

I_3 = I_0 (0.9)^3(3/4)^3

I_3 = 30.75

w/m

^{2}

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