Interference of light obeys the Principle of conservation of:

The correct answer is Option (4) → Energy

In interference light waves superpose, and the energy is not created or destroyed: it is only redistributed from the dark fringes to the bright fringes, so the total energy is conserved.

NCERT (2026-27):
Seeing the Single Slit Diffraction Pattern – “… In interference and diffraction, light energy is redistributed. If it reduces in one region, producing a dark fringe, it increases in another region, producing a bright fringe. There is no gain or loss of energy, which is consistent with the principle of conservation of energy.”