question_answer

Directions (Q. Nos. 28): For the following questions. Choose the correct answers from the codes [a], [b], [c] and [d] defined as follows.

Statement I In Doppler effect, if the detector is stationary and the source is moving with constant velocity, then the apparent frequency as received by detector must be constant.

Statement II In Doppler effect expression, \[{{f}_{AP}}=f\,\left[ \frac{v-{{v}_{d}}}{v-{{v}_{s}}} \right],\] where symbols have their usual meanings, \[{{v}_{s}}\] represents the component of velocity of source along the line joining source and detector, at the instant when source emits the wave which is received by detector at some later instant \[{{t}_{0}}\], and at this instant the detector receives the frequency \[{{f}_{AP}}\].

A)  Statement I is true. Statement II is also true and Statement II is the correct explanation of Statement I.

B)  Statement I is true. Statement II is also true and Statement II is not the correct explanation of Statement I.

C)  Statement I is true. Statement II is false.

D)  Statement I is false. Statement II is true.

Correct Answer: D

Solution :

 In shown case, detector is stationary while source is moving with constant velocity but the frequency as received by detector is changing as component of velocity of source along the line joining source and detector is changing.