Question

Is light a ray or a wave?

Answer 1

Light is known to have a dual-nature, that is it travels both in the form of waves and particles(photons). And it always(general cases) travels is a straight line.

The book must have used the term ‘rays’ to say that light propagates(travels) in that direction in a straight line.

So light rays mean the same as waves or particles.

hope this helps....

Answer 2

Now that the dual nature of light as "both a particle and a wave" has been proved, its essential theory was further evolved from electromagnetics into quantum mechanics. Einstein believed light is a particle (photon) and the flow of photons is a wave.