phase difference and path difference?

Question

what is phase difference and path difference? please help because i often found the term in subjects dealing with light

Answer 1

The wave length is the distance between two consecutive points which are in same phase.

The wave pattern repeats itself after one wavelength.

Thus we can consider this as one cycle of operation.

One cycle corresponds to 2pi radian or 360 degree.

Thus a wave length ( Lambda) corresponds to 2pi radian

Any orbitrary length l corresponds to( 2 pi/ lambda ) x l

The path differnce l is equivalent to a phase difference of ( 2 pi/ lambda ) x l

A phase difference of Theta corresponds to a path difference of ( Lambda/2pi ) x theta.