‘Beats’ is a phenomenon that occurs when frequencies of two harmonic w

‘Beats’ is a phenomenon that occurs when frequencies of two harmonic waves are

equal.
far apart.
multiples of each other.
nearly same.
This question was previously asked in
UPSC NDA-1 – 2021
The correct answer is (D) nearly same.
‘Beats’ is a phenomenon that occurs when two waves of slightly different frequencies interfere with each other. This interference results in periodic variations in the intensity of the combined wave, heard as a waxing and waning of sound (or seen as flickering in light).
The beat frequency is the difference between the frequencies of the two individual waves (f_beat = |f1 – f2|). For distinct beats to be perceived, the frequency difference must be relatively small (typically less than about 7-10 Hz for sound waves). If the frequencies are exactly equal, they interfere constructively or destructively to produce a wave of constant amplitude. If the frequencies are far apart, the rapid variations in intensity are not perceived as beats.