Fringe spacing for reflected fringes in a wedge ≈ λ/(2α) = 6×10⁻7/(2×0.01)=3×10⁻5 m = 0.03 mm; 10th dark fringe at 10×0.03 mm = 0.30 mm.

Diffraction patterns result from superposition of many wavelets and can be understood as a form of interference of those wavelets.

With intensities 9 and 1, amplitude ratio is 3:1; Imax/Imin = (3+1)^2/(3-1)^2 = 16/4 = 4:1, so option C is correct.

With intensities 16 and 9, amplitudes are 4 and 3; Imax/Imin = (4+3)^2/(4-3)^2 = 49/1 = 49:1.

Beats arise from alternating constructive and destructive interference between two nearby frequencies.

Grating element (spacing) a is total length divided by number of lines, so a = L/N.

Answer taken from block header hint for this block.

Coherent sources maintain a constant phase relationship and the same frequency, so both conditions hold.

The block gives the explanatory answer C; fringe spacing is inversely proportional to d and directly proportional to L (Ay = λL/d).

The angular width of the central maximum depends on wavelength and slit width (θ ≈ λ/a) and not on the distance between the slit and the source.