# Waves and sound

Hi guys. Was studying waves and got a bit confused. Pl help me out.

Coherent sources are those which produce waves of same frequency, wavelength and velocity. Amplitude need not necessarily be same. Am I right?

There's another doubt in my mind...

If two waves produce beats then which of the following quantities are necessarily same for both of them
Angular wave number( and thus wavelength)
Angular frequency ( and thus frequecy)
Velocity of wave
Amplitude

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For coherence, they must have the same phase relationship. At least during the coherence time.
The wavelength depends on frequency and phase velocity so it is not an independent quantity.

For beats you need to have slightly different frequencies. Amplitudes can be different but then the minims won't be zero.

For coherence, they must have the same phase relationship.
What do you mean by same phase relationship?
Is my notion about coherent waves correct?

Angular wave number( and thus wavelength)
Angular frequency ( and thus frequecy)
Velocity of wave
Amplitude
So none of these have to be necessarily same for 2 waves to produce beats?

sophiecentaur