1. A car moves with a speed of 54km/h towards a cliff.The horn of the car emits a frequency of 400Hz at a speed of 335m/s
(a)Find the wavelength of the sound emitted by the horn in front of the car
(b)Find the wavelength of the wave reflected from the cliff
(c)What frequency does a person sitting in the car hear for the reflected sound wave?
(d)How many beats does he hear in 10 secs between the sound coming directly from the horn and that coming after reflection?
2. An operator sitting in his base camp sends a sound signal of frequency 400Hz. The signal is reflected back from a car moving towards him . The frequency of the reflected sound is found to be 410 Hz. Find the speed of the car when the speed of sound in air is 324m/s.
Doppler's Effect equations.
The Attempt at a Solution
I had no problem in finding out the a,b,c but have a problem in finding out part d.The answer says that there would be no beat frequency heard...how could that be when it is receiving two distinct frequencies (source, reflection)
In the second question, the answer is 12m/s, but i got it as 3m/s...how is that?