When beats are produced by two progressive waves of nearly the same frequency, which one of the following if correct?

Options

A. the particle vibrate simple harmonically with the frequency equal to the difference in the component frequencies.
B. The amplitude of vibration at any point changes simple harmonically with a frequency equal to the difference in the frequencies of the two waves.
C. The frequency of beats depends upon the position, where the observer is.
D. The frequency of beats changes as the time progresses.

Answer

B

Explanation

As `y=A_bsin(2pin_(av)t)`
where `A_b=2Acos(2pin_At)`
where `n_A=(n_1-n_2)/(2)`
Hence, the amplitude f vibration at any point changes simple harmonically with a frequency equal to the difference in the frequencies of the two waves.