A passenger is sitting in a train which is moving fast. The engine of the train blows a whistle of frequency ' n '. If the apparent frequency of sound heard by the passenger is ' f ' then
The situation described involves the Doppler effect, but with a key distinction: both the source of the sound (the train's engine) and the observer (the passenger) are moving at the same speed in the same direction since they are both on the train. In the Doppler effect, the frequency of a wave changes due to the relative motion between the source and the observer. However, if the source and the observer are moving together at the same velocity (as is the case here with the passenger and the train's engine), there is no relative motion between them. Consequently, the frequency of the sound heard by the observer (passenger) will be the same as the actual frequency of the sound emitted by the source (train's engine). Therefore, the correct answer is : Option A:f=n