When a train approaches a stationary observer, the apparent frequency of the whistle is n' and when the same train recedes away from the observer, the apparent frequency is n ". Then, the apparent frequency n when the observer moves with the train is-

see full answer

Your Exam Success, Personally Taken Care Of

1:1 expert mentors customize learning to your strength and weaknesses – so you score higher in school , IIT JEE and NEET entrance exams.

An Intiative by Sri Chaitanya

answer is D.

(Unlock A.I Detailed Solution for FREE)

Best Courses for You

JEE

NEET

Foundation JEE

Foundation NEET

CBSE

Detailed Solution

Concept- In this question, we will look at two separate scenarios and solve them with different figures. We will use the apparent frequency formula in both cases and then add them after simplifying as requested by the question.
The frequency given by the question is

.
Case

As we all know, the apparent frequency formula is Question Image

. Where

is the actual frequency,

is the observed frequency,

is speed,

is velocity of the observer and

is the velocity of the source.
Here,

Thus, the equation for n' will be_
Question Image

Let the above equation be equation 1 –
Question Image

(Equation 1)
Case 2-
Here,

The indicators will be inverted since the source is moving away from the observer. Question Image