If sinθ1 = λ/d = sin32° ≈0.5299, then sinθ2 = 2λ/d ≈1.0598 >1, so second order is not possible.

X-ray wavelengths are on the order of a few angstroms, so grating spacings of a few angstroms produce diffraction.

Newton's rings arise from interference between light reflected from two surfaces separated by a thin air film.

For equal slit sources and zero path difference, the centre corresponds to constructive interference producing a bright fringe.

Beat frequency equals the frequency difference n, so in two seconds the number of beats is 2n.

Colours in thin films arise from interference between light reflected from the film's different surfaces.

In Young's double-slit interference with ideal conditions, bright and dark fringes have equal widths, corresponding to alternate maxima and minima.

Fringe separation y = λL/d = (589×10⁻⁹ m)(2.25 m)/(1×10⁻³ m) ≈ 1.33×10⁻³ m, which equals about 1.33 mm, so both representations match (option C).

Fringe width β ∝ 1/d, so halving d doubles β, hence option A.

Shift = (μ−1)t/λ = 0.5×2×10⁻4 /5×10⁻7 = 200 fringes, so none of the given small values is correct.