Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Questions 11.5, 11.6, 11.8
Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:
A wave has a frequency and wavelength of 200 Hz and 0.75 m, respectively. If the frequency of the wave source is changed, which wave parameters(s) will change as a result?
(A The wavelength.
(B) The speed of the wave.
(C) (Both of the above choices.)
(D) (None of the above choices.)
(E) (I'm lost, and don't know how to answer this.)
Sections 30880, 30881
(A) : 20 students
(B) : 4 students
(C) : 9 students
(D) : 1 students
(E) : 0 students
This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.
Sections 30880, 30881
(A) : 25 students
(B) : 2 students
(C) : 6 students
(D) : 0 students
(E) : 0 students
Correct answer: (A)
The frequency f of a wave is determined solely by the properties of the source, while the wave speed v is determined solely by the properties of the medium (thus frequency and wave speed are said to be the independent wave parameters). The wavelength is the dependent wave parameter that is determined by both the source and medium, given by:
lambda = v/f or v*T,
where T is the period (which is the inverse of frequency). So if frequency changes, the wave speed will still remain constant, but the wavelength will as a result change.
Pre- to post- peer-interaction gains:
pre-interaction correct = 59%
post-interaction correct = 76%
Hake, or normalized gain
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