Question

the phase difference Ф is related to path difference Δx by

Answer 1

lamda by 2π into phi

Answer 2

"Phase difference" is related to the path difference by the relation of lambda and angle.

$\Delta X=\frac{\lambda \cdot \Delta \phi}{2 \pi}$

This relation denotes relation of the phase difference and path difference.

The "phase difference" is the difference existing between two waves which has same frequency with reference to time having same point of reference.

The "path difference" is the difference existing between path lengths of two waves which has same frequency with reference to velocity having equal magnitude."