Physics quiz question: comparing light speeds

Physics 205B Quiz 7, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 26.3.

A Physics 205B is moving at a constant velocity to the right. Two lights are simultaneously trigged to flash (in the rest frame of the lights) when student is midway between them. According to the Physics 205B student, the speed of the flash from the right light is __________ the flash from the left light.
(A) faster than.
(B) slower than.
(C) the same as.
(D) (Not enough information is given.)

Correct answer: (C)

From Einstein's second postulate of special relativity, the speed of light is invariant and independent of the relative motion of the observer and source.

Student responses
Section 70856
(A) : 3 students
(B) : 0 students
(C) : 8 students
(D) : 0 students

Success level: 72%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33