NEET Physics Notes Waves-Beats
Beats
Beats
When two sound waves of nearly equal (but never equal) or slightly different frequencies and equal or ^nearly equal amplitudes travelling along the same direction superimpose at a given point, the resultant sound intensity alternately rises and falls. This alternate rise and fall of sound at a given position is called beats.
Number of beats formed per second is called the frequency of beats. If two sound waves of frequencies v1 and v2 superimpose, then frequency of beats = 
For formation of distinct beats, then difference between the frequencies of two superposing notes should be less than 10 Hz.
If source of sound is linear, then at a distance d from the line source
Our perception of loudness is better co-related with the second level measured in decibel (dB) and defined as follows
We can find true frequency of tuning fork B from a pair of tuning forks A and B, in which frequency of A is known, where x is the beats per second
Doppler’s Effect
The phenomena of apparent change in frequency of source due to a relative motion between the source and observer is called Doppler’s effect.
