Cuesta College, San Luis Obispo, CA
Unpolarized light passes through two polarizers with polarization axes turned as shown below.
The fraction of the incident light intensity transmitted is:
Correct answer (highlight to unhide): (C)
The intensity of light that passes through polarizer 1 is one-half of the original unpolarized intensity, and this light is then diagonally polarized, having a polarization that matches the transmission axis of that polarizer, at an angle of 30° measured clockwise from the vertical (the convention followed in this class is to depict transmission axes of polarizers).
The fraction of this diagonally polarized light that passes through polarizer 2 is cos2θ, where the angle θ = 10° is measured between the diagonal polarization of the light entering polarizer 2 (30° clockwise from vertical) and the transmission axis of polarizer 2 (40° clockwise from the vertical).
Thus the fraction of the light that passes through both polarizer 1 and polarizer 2 is:
(1/2)·cos2(10°) = 0.48492315519...,
or to two significant figures, 0.48 of the original unpolarized intensity.
(Response (A) is (1/2)·cos2(40°); response (B) is (1/2)·cos2(30°); and response (D) is cos2(10°).)
Sections 30882, 30883
Exam code: quiz01Om6A
(A) : 15 students
(B) : 3 students
(C) : 7 students
(D) : 3 students
Success level: 25%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43