How do we know that light is a wave?
Waves spread out either as wavefront or as spherical wave.
Wave character of light is established, when light
shows diffraction
.
Examples for diffraction are the interference patterns of a single , double or multiple slit experiment.
Interference grating is a phenomenon, when light is diffracted by very many slits (more than 1000 per cm). Then white light is decomposed into the spectral colors.
Watch light reflecting from a CD or DVD: you see many colors. The reason is that the tracks act like a very many fine slits.
Other properties of light showing its wave character?
Refraction (light will bend) ---> Optics
Simulation to understand interference of waves:
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