In a Young’s double-slit set-up, the slits are 0.40mm apart and are illuminated with light of wavelength 520nm. Initially the screen is placed 0.80m from the slits and no additional material is present.
Later, two simultaneous changes are made:
1. The screen is moved away from the slits so that its distance becomes 1.0m.
2. A transparent plate of thickness 2.0μm and refractive index 1.60 is introduced in front of the same slit as in part (1).
(i) Calculate the displacement of the central bright fringe on the new screen due to moving the screen alone.
(ii) Calculate the displacement of the central bright fringe that would be produced on the original screen if only the plate were introduced.
(iii) Hence find the net linear shift (magnitude and direction) of the central bright fringe on the screen in its new position after both changes are applied together.