A ray of light is always

The correct answer is Option (1) → normal to the wavefront

A ray is the path along which the energy of the wave travels, and the energy travels perpendicular to the wavefront.

Option (1) normal to the wavefront — Correct. Since the wavefront moves forward at right angles to itself, every ray is perpendicular to the wavefront at the point where it crosses it. For a plane wave the rays are parallel lines normal to the plane wavefronts.

Option (2) parallel to the wavefront — Incorrect. A line along the wavefront joins points of the same phase. The wave does not advance along it, so no energy flows in that direction.

Option (3) away from the wavefront — Incorrect. A line leaving the wavefront at a slant also points away from it. But the ray has one definite direction, at \( 90^\circ \) to the wavefront.

NCERT (2026-27):
Introduction – “… Indeed, the branch of optics in which one completely neglects the finiteness of the wavelength is called geometrical optics and a ray is defined as the path of energy propagation in the limit of wavelength tending to zero.”

Huygens Principle – “… The speed with which the wavefront moves outwards from the source is called the speed of the wave. The energy of the wave travels in a direction perpendicular to the wavefront.”