Physics quiz question: wavelength, frequency, and wave speed

Physics 205A Quiz 6, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 11.12

A wave has a frequency and wavelength of 220 Hz and 0.58 m, respectively. What is the speed of the wave?
(A) 2.6e-3 m/s.
(B) 7.8e-3 m/s.
(C) 130 m/s.
(D) 380 m/s.

Correct answer: (C)

The wave speed is v = lambda/T = lambda*f = (0.58 m)*(220 s^-1) = 127.6 m/s, which is 130 m/s, to two significant figures. Response (A) is lambda/f; response (B) is 1/(lambda*f); response (D) is (f/lambda).

Student responses
Sections 70854, 70855
(A) : 12 students
(B) : 1 student
(C) : 29 students
(D) : 7 students

Success level: 59%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.85

Student responses
Section 72177
(A) : 1 student
(B) : 0 students
(C) : 10 students
(D) : 1 students

Success level: 83%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33