Periodic Motion : Motion which is repeated after regular interval of time. Ex: Earth's rotation or revolution.
SHM : A motion which has single frequency and constant amplitude . Ex : Movement of a Top.
Virbratoy Motion : An upward and downward movement of a body or a string is called vibratory motion Ex. Earth quake, guitar string etc.
(i) Phase : Phase is the state or position of the particle in a medium or a wave
Here in the above diagram , the particle at A is at an angle of `pi/2(90^(@))` . So the phase is `pi/2(90^(@))` . i.e. (`90^(@)+45^(@))`
Phase difference : Consider two waves which are the disturbances produced by two particles at different instants of time . The difference in phase between the two particles (making two different waves) is called phase difference if phase difference is zero, then the two waves are said to be in phase if the two waves have a phase difference then two waves are out of phase .
Phase difference : For one full cycle of a wave, the wavelength is `lamda`
Wavelength can also be defined as the distance between can also be defined as the distance between two consecutive crests ot troughs in a wave.
(ii) In the diagram 1 :
The phase difference is zero. i .e the two waves are in phase . All particles between these two waves are moving with the same time and same angle at different point . The path difference is also zero.
In the diagram 2 :
Wave - 1 starts before wave -2 and they meet at a point in line with each other at an angle of `pi/2`
So the phase difference between waves 1 & 2 `pi/2` . The path difference is `(lamda)/(4)`
In the diagram 3 :
Wave - 1 and wave 2 are moving in opposite direction and meet at an angle of `pi` initially . So the phase difference is `pi` and the path difference is `(lamda)/(2)`.
