Draw a ray diagram to show how a ray of light passes through a parallel-sides glass block if it hits the glass at an angle litter than 90° (that is, obliquely to the glass)

Explanation:

When a ray of light hits a glass block at an angle less than 90 degress, this is olbiquely, it passes through the glass block with a different angle, which is known as the refraction of the ligtht

This is, the ray of light will bend: it will change the angle with respect to the normal of the surface of the glass block.

The amount the angle changes depend on the relative index refractions of the two media: for instance, the air, from which the ray of ligth comes from, and the glass.

Since the index of refraction of the glass is greater than the index of refraction of air, the ray of light will move away from the direction of the normal.

The refraction happens because the speed of light on both media are different.

When the ray of light has passed through the entire block and emerges again in the air, on the other side of the block, the ray of ligth will again experience refraction, and bends exactly the same amount, but moving away from normal. So, when the surfaces of the glass block are parallel, the ray of light will emerge in a direction parallel to that it initially entered.