In a Lloyds's mirror experiment as narrow slit S transmitting a light of wavelength `lambda` is placed 3 mm above a small plane mirror ( as shown). The light coming directly from the the slit and that coming after the reflection interfere on a screen placed at a distance of 90 cm from the slit. Length of mirror is 2 mm and the middle point of mirror is 2 mm from point P.

If the mirror is shifted towards left then how does the fringe pattern on screen changes ?

Options

A. fringe width decreases and the region in which interference is formed shifts downwards
B. fringe width decreases and the region in which interference is formed shifts upwards
C. fringe width does not change and the region in which interference is formed shifts upwards
D. fringe width does not change and the region in which interference is formed shifts downwards

Answer

C