question_answer

The Doppler shift in the frequency received by a stationary receiver when the source is moving towards it, was measured to be\[\Delta {{v}_{air}}\]when both receiver and source are in air, and it was measured to be\[\Delta {{v}_{water}}\]when both are under water. Then,

A)  \[\Delta {{v}_{air}}>\Delta {{v}_{water}}\]

B)  \[\Delta {{v}_{air}}<\Delta {{v}_{water}}\]

C)  \[\Delta {{v}_{air}}=\Delta {{v}_{water}}\]

D)  \[\Delta {{v}_{water}}=0,\Delta {{v}_{air}}<0\]