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1.
v = n l =
l
where v is the velocity, n is the frequency, T is period of a wave, l is the wave length of the wave.
T
2.
Equation of a simple harmonic progressive wave travelling in the positive direction of the xaxis,
y = A sin 2p(
t

x
) = A sin
2 p
(Vt  x)
3.
For a simple harmonic wave travelling in the negative direction of the xaxis,
(the equation is y = A sin 2p(
+
(Vt + x)
4.
If two sources of sound have frequencies n_{1} and n_{2}, the number of beats per second is ( n_{1}  n_{2} ) .
i.e. n =  n_{1}  n_{2} 
5.
Phase difference between two particles which are separated by distance, x =
2px
6.
Velocity of a wave v = nl
Velocity of a particle at a distance 'x' from origin which executes SHM is given by v_{p} =
dy
dt
or v_{p} = w
7.
When one of the prongs of the tuning fork is filed, its frequency increases.
8.
When one of the prongs of the tuning fork is loaded, its frequency decreases.
9. Doppler Effect:
n_{a}_{ }
V
when source is moving towards a stationary observer.
V  S
when source is moving away from a stationary observer.
V + S
n(V + L)
when listener is moving towards stationary source.
n(V  L)
when listener is moving away from a stationary source.
n_{a}_{ }= apparent frequency n = actual (or true) frequency s = velocity of source L = velocity of listener V = velocity of sound.
10. Include the Cases:
What happens to the frequency when prongs are filed and loaded? When the prongs of the fork are loaded, the frequency of the fork decreases. When the prongs of the fork are filed, the frequency of the fork increases.