Cuesta College, San Luis Obispo, CA
Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.
(The following question was asked subsequent to the lecture on Doppler shifts.)
Suppose you are standing on the sidewalk as a car, with its horn continuously on, comes from behind you, passes by, and continues on ahead of you. How does the pitch of the car horn change as this happens? (Graded for completion.)
(A) Its pitch starts out high, then drops lower.
(B) Its pitch starts out low, then goes higher.
(C) Its pitch is low, goes higher, then drops back down to low.
(D) Its pitch is high, goes lower, then goes up to high.
(E) (I'm lost, and don't know how to answer this.)
Student responses (pre-test, all responses)
Sections 70158, 70160
(A) : 8 students
(B) : 2 students
(C) : 59 students
(D) : 1 student
(E) : 2 students
Correct answer: (A)
Students seemed to conflate pitch (frequency) with loudness (intensity). Because of these responses, students were then shown the following video at the start of class, and told to discuss in a think-pair-share format what happens to pitch rather than loudness before answering again using flashcards.
http://video.google.com/videoplay?docid=-7337076920663696115&q=doppler+effect&total=213&start=0&num=10&so=0&type=search&plindex=0
Students demonstrate the change in frequency that occurs as a car blowing its horn moves by an observer (Delsea Regional High School, Franklinville, NJ).
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