Two in-phase point sources of water waves are apart and emit waves of frequency
PHYSICS · Single correct · A Level · Physics · Waves · Waves
Problem
Two in-phase point sources of water waves are 3.0m apart and emit waves of frequency 5.0Hz. The wave speed on the pond surface is 1.5ms−1. A small float is positioned 4.0m from one source and 5.0m from the other. Which of the following best describes the motion of the float caused by the arriving waves?
(a) The float experiences minimum amplitude because the waves arrive about 180∘ out of phase, giving almost complete cancellation.
(b) The float rises and falls in beats at 2Hz because the differing path lengths make the two waves effectively different frequencies.
(c) The float experiences an intermediate amplitude because the waves arrive with a phase difference of about 120∘.
(d) The float experiences maximum amplitude because the path difference is an integer multiple of the wavelength, so the waves are in phase.