What is a ray of light?

At what angle ,a ray of light will incident on one face of an equilateral prism,so that the emerget ray may graze the second surface of the prism(=1.5)?

What is the cause of change in direction of a ray of light on refraction?

At what angle should a ray of light be incident on the face of a prism of refracting angle 60^@ so that it just suffers total internal reflection at the other face? The refractive index of the material of the prism is 1.524.

When a ray of light enters a glass slab,then

When a ray of light passes through a glass prism then a spectrum is obtained on the screen Draw a diagram showing a spectrum of white light.

A monochromatic ray of light is made to fall on a normal 60^@ prism under minimum deviation condition.What is the relatin between the angle of incidenc eand the angle of emrgence?