Explain how Corpuscular theory predicts the speed of light in a medium, say, water, to be greater than the speed of light in vacuum. Is the prediction confirmed by experimental determination of the speed of light in water ? If not, which alternative picture of light is consistent with experiment?

Explanation

According to corpuscular theory when light enters denser medium from a rarer medium, then the particles of light experience force along the normal to the surface. This increases velocity component along the normal. The component of velocity along the surface remains unchanged. Hence overall velocity increases when light goes into denser medium from rarer medium. But this prediction is contradictory to experimental observations.