A speeding motorcyclist sees traffic jam ahead of him. He slows down to 36 km `cdot H^(-1) `. He finds that traffic has eased and a car moving ahead of him at `18 km cdot h^(-1) ` is honking at a frequency of 1392 Hz. If the speed of sound is 343 `m cdot s^(-1)`, the frequency of the honk as heard by him will be

Options

A. 1332 Hz
B. 1372 Hz
C. 1412 Hz
D. 1454 Hz

Answer

C

Explanation

Speed of motorcyclist, `u_(o)=36" km" cdot h^(-1)=10m cdot s^(-1)`
Speed of car, `u_(s)=18" km" cdot h^(-1)=5m cdot s^(-1)`
Now, fundamental frequency of honk, v = 1392 Hz
`therefore lambda. = (V+u_(s))/n=(343+5)/1392=0.25 m `
Hence, frequency of honk as heard by the cyclist
`(V+V_(0))/(lambda.)=(343+10)/0.25=1412` Hz
The option (c) is correct.