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.