When waves reinforce at every point, they exhibit constructive interference, producing a larger resultant amplitude.

Light is an electromagnetic wave and does not require a material medium, so it is not a mechanical wave.

In standing waves the kinetic and potential energy densities are greatest at antinodes, so energy is maximum at anti-nodes.

Only transverse waves can be polarized, so polarization indicates that light behaves as transverse waves.

Using E = p^2/(2m) with p = h/λ gives E = h^2/(2mλ^2) ≈ 0.51 eV for a proton with λ = 0.4 Å.

The Doppler effect describes the change in observed frequency due to relative motion between source and observer.

Energy carried by a wave (e.g., intensity) is proportional to the square of its amplitude.

Plucking a string perpendicular to its length produces displacements transverse to the string, creating transverse waves.

Sound waves are mechanical pressure waves, not electromagnetic radiation, so option D is not electromagnetic.

Reflection from a rarer medium does not invert the phase, so the phase change is 0°.