White light produces fringes of different wavelengths that overlap, yielding a bright white central fringe with coloured and blurred fringes further out.

Covering one slit removes the second coherent source, eliminating interference fringes and producing essentially uniform illumination (no two-source interference).

Fringe width β = λD/d, so halving slit separation d doubles the fringe width.

Fringe width in diffraction varies inversely with slit width (wider slit → narrower fringes).

Infrared photons have less energy than visible photons (E = hc/λ), so statement A is false and thus the wrong statement.

The explanatory answer in the block states option C; decreasing slit separation d increases fringe width (Ay = λL/d).

Fringe spacing β = λD/d depends on wavelength λ, screen distance D, and slit separation d, so all listed factors affect it.

A typical transmission grating has opaque lines with transparent spacing between them, so the spacing is transparent.

Bragg's law for diffraction by crystal planes is 2d sin θ = nλ, so option C is correct.

White light disperses into the seven constituent spectral colours (VIBGYOR) when diffracted by a grating, commonly referenced as seven colours.