an observer is moving with an constant speed of 20m/s on an circular track of radiusb50m.A source kept at centre of the track emits a sound of frequency 200m.Then the frequency heard by the observer??
Answers
Answer:
Key Idea the perceived frequency heard by the observer depends upon the relative motion between observer and source.
If the source and observer are approaching each other, then the velocity of the source v
s
is positive and velocity of the listener v
l
is negative, the perceived frequency will be higher than the original.
Perceived frequency is given by
n
′
=n(
v−v
0
v+v
0
) [∵n
′
=n
v−v
s
v−(−v
0
]
Here, v=340m/s,v
0
=20m/s,
v
s
=20m/s,n=240Hz
Hence, n
′
=240(
340−20
340+20
)
=240×
320
360
=270Hz
Note When the speed of source and observer are much lesser than that of sound, the change in frequency becomes independent of the fact whether the source is moving or the observer.
Explanation: