Question

A small vibrating object S moves across the surface of a ripple tank producing the wave fronts shown above. The wave fronts move with speed v. The object is traveling in what direction and with what speed relative to the speed of the wave fronts produced?

	Direction	Speed
(A)	To the right	Equal to v
(B)	To the right	Less than v
(C)	To the right	Greater than v
(D)	To the left	Less than v
(E)	To the left	Greater than v

Answer 1

The correct option is: (B)

Explanation:

Doppler effect. The waves at right are compressed because the object is moving right. However, the waves are moving faster than the object since they are out in front of where the object is.