Two wavefronts separated by a distance of `lambda//2` have a phase difference of -

Light waves of wave length lambda propagate in a medium. If M end N are two points on the wave front and they are separated by a distance lambda"/"4 , the phase difference between them will be (in radian)

Two point on a plane wavefront corresponding to lambda=5000 Å are separated by a distance of 2mm. What is the phase difference between those points?

The phase difference between oscillatory motion of two points separated by a distance of lamda/2 is ( where lamda is the wavelength)

The phase difference between oscillatory motion of two points separated by a distance of lamda/2 is ( where lamda is the wavelength)

Express path difference of lambda/2 in terms of phase difference.