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Date May 2013 Marks available 1 Reference code 13M.1.HL.TZ1.17
Level Higher level Paper Paper 1 Time zone Time zone 1
Command term Question number 17 Adapted from N/A

Question

Unpolarized light of intensity I0 is transmitted through a polarizer which has a transmission axis at an angle θ to the vertical. The light is then incident on a second polarizer with a transmission axis at an angle ϕ to the transmission axis of the first polarizer, as shown below.

 

 

The intensity of the light that emerges from the second polarizer is I. What is the ratio \(\frac{I}{{{I_0}}}\)?

A. 0.25

B. 0.5 cos2 (θ+φ)

C. 0.5 cos2 φ

D. cos2 θ cos2φ

Markscheme

C

Examiners report

When unpolarized light passes through a polarising filter its intensity halves. Clearly all angles of the polarising filter are logically equivalent and therefore immaterial. However, when polarized light passes through a polarizing filter its intensity is reduced depending upon the angle of the filter to the plane of polarization. Hence C is the only logically possible answer. The most popular response, however, was D, presumably since the candidates referred to their formula booklets before thinking through the situation illustrated.

Syllabus sections

Core » Topic 4: Waves » 4.2 – Travelling waves
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