Lloyd's MirrorHardQuestion 20240
Question
In Lloyd's mirror experiment, the fringe at the edge (zero path difference) is:
- ABright (constructive)
- BDark (destructive) due to phase change on reflectionCorrect
- CAbsent
- DWhite fringes only
Correct answer
Dark (destructive) due to phase change on reflection
Explanation
The reflected ray undergoes a phase change of π (half wavelength) on reflection from the denser glass mirror. At zero path difference, the direct and reflected beams are π out of phase → destructive interference → dark fringe at the edge. This confirms the phase change on reflection.