## 20121123

### Physics quiz question: decreasing frequency of wave source

Physics 205A Quiz 6, fall semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Questions 11.5, 11.6

A periodic wave has a speed and wavelength of 70 m/s and 0.30 m, respectively. If the frequency of the wave source is decreased, the __________ would increase.
(A) wave speed.
(B) wavelength.
(C) (Both of the above choices.)
(D) (Neither of the above choices.)

Correct answer (highlight to unhide): (B)

Wave speed v depends on the properties of the medium. Frequency f depends on the properties of the source. These two parameters can be varied independently of each other.

The wavelength λ is the parameter dependent on both of the independent parameters:

λ = v/f,

such that decreasing the frequency f of a wave source will not affect the wave speed v, but will cause the wavelength λ to increase.

Sections 70854, 70855
Exam code: quiz06How3
(A) : 1 student
(B) : 38 students
(C) : 1 student
(D) : 6 students

Success level: 85%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20