What does the phenomenon of interference prove about light?

The correct answer is Option (2) → That it has a wave nature

Option (1) That it has a particle nature — Incorrect. Particles arriving at a point can only add up. They cannot leave a dark fringe at a point where light from both sources falls.

Option (2) That it has a wave nature — Correct. In interference, light from two coherent sources adds up at some points to give bright fringes and gives zero intensity at others, the dark fringes. Such superposition is a property of waves. Young’s interference experiment of 1801 firmly established that light is a wave.

Option (3) That its energy travels in packets called photons — Incorrect. The photon picture comes from the photoelectric effect, which shows the particle nature of radiation. The wave picture explains interference fringes.

Option (4) That the higher the frequency, the more energy the wave carries — Incorrect. The energy \( h\nu \) rising with frequency belongs to the photon picture. In the wave picture the intensity depends on the square of the amplitude. Interference only shows how this energy is shared between bright and dark fringes.

NCERT (2026-27):
Introduction – “… However, when Thomas Young performed his famous interference experiment in 1801, it was firmly established that light is indeed a wave phenomenon.”