Wave Optics

Is NCERT enough for Wave Optics in JEE?

NCERT is largely sufficient: Huygens' principle, Young's double-slit experiment, single-slit diffraction and polarisation are asked close to the textbook. Practise YDSE variations (a glass slab in one slit, a changed medium) from PYQs.

Common JEE questions on Wave Optics

What is the fringe width in Young's double-slit experiment?

β = λD/d. Immersing the set-up in a medium of refractive index μ reduces it to β/μ.

What happens when a thin film is placed over one slit?

The whole pattern shifts towards that slit by (μ − 1)t·D/d; the fringe width does not change.

How is diffraction different from interference?

Interference comes from two coherent sources and gives equally bright fringes. Diffraction comes from one wavefront and has a wide central maximum with fading secondary maxima.

What is Malus's law?

I = I₀cos²θ for light passing through an analyser at angle θ to the polariser.