A source of sound S emitting waves of frequency 100 Hz and an observer O are located at some distance from each other. The source is moving with a speed of 19.4 ms-1 at an angle of 60° with the source observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air 330 ms-1), is:
103 Hz
106 Hz
97 Hz
100 Hz
As discussed in
frequency of sound when source is moving towards the observer and observer is moving away from source -
- wherein
Speed of sound
Speed of observer
speed of source
Original frequency
apparent frequency
From Doppler's effect,
Option 1)
103 Hz
This option is correct
Option 2)
106 Hz
This option is incorrect
Option 3)
97 Hz
This option is incorrect
Option 4)
100 Hz
This option is incorrect