Two In-Phase Loudspeakers Are 3

Multiple Choice

Two in-phase loudspeakers are 3.0 m apart.They emit sound with a frequency of 490 Hz.A microphone is placed half-way between the speakers and then moved along the line joining the two speakers until the first point of constructive interference is found.At what distance from that midpoint is that first point? The speed of sound in air is 343 m/s.

A) 0.18 m
B) 0.35 m
C) 0.50 m
D) 0.70 m
E) There is no point in that line where constructive interference occurs.