Light travels more quickly through water than through glass.(a) Which is optically denser : water or glass?(b) If a ray of light passes from glass into water, which way will it bend : towards the normal or away from the normal?

(a) Glass is optically denser as compared to water.

(b) If a ray of light passes from glass into water, it will bend away from the normal because glass is a denser medium as compared to water.

Explanation

The angle of refraction or the amount of bending of light depends on the refractive index  of the two media.

1. When light passes through a low refractive index, like air (faster medium or optically rarer medium) to a high refractive index, like glass(slower medium or optically denser medium), its speed decreases and bends towards the normal. 

2. When light passes through a high refractive index, like glass (slower medium or optically denser medium) to a low refractive index, like air (faster medium or optically rarer medium) its speed increases and bends away from the normal.