Two waves of slightly different frequencies `f_(1) and f_(2) (f_(1) gt f_(2))` with zero phase difference , same amplitudes ,travelling in the same direction superimpose .

Options

A. Phenomenon of beats is always observed by human ear.
B. Intensity of resultant wave is a constant.
C. Intensity of resultant wave varies periodically with time with maximum intensity `4 a^(2)` and minimum intensity zero.
D. A maxima appears at a time `1//[2 (f_(1) - f_(2))]` later ( or earlier ) than a minima appears .

Answer

C, D

Explanation

`t = 0 , (1)/((f_(1) - f_(2))) , (2)/((f_(1) - f_(2))) , (3)/((f_(1) - f_(2))) ,…..`
are times at which maxima are obtained
`t = (1/2)/((f_(1) - f_(2))) , (3/2)/((f_(1) - f_(2))) , (5/2)/((f_(1) - f_(2))) ,…`
are times at whhich minima are obtained.