Physics 205B Quiz 3, spring semester 2010
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Example 25.1, Problem 25.1
Two coherent, in-phase 5.0 MHz radio transmitters are located along an east-west line, separated by a distance of 150 m. A receiver located due west of these transmitters will detect __________ interference.
(A) constructive.
(B) destructive.
(C) something in-between constructive and destructive.
(D) (Not enough information is given.)
Correct answer (highlight to unhide): (B)
The wavelength is given by λ = c/f = (3.00×108 m/s)/(5.0×106 s–1) = 60 m. The path difference between the waves that are emitted by these in-phase towers, in the west direction, is ∆l = 150 m, which is equal to (150 m)/(60 m) = 2.5·λ, and thus there is destructive interference.
Student responses
Section 31988
(A) : 6 students
(B) : 5 students
(C) : 0 students
(D) : 0 students
Success level: 45%
Discrimination index (Aubrecht & Aubrecht, 1983): 1.00
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