What happens to light rays when they pass through objects such as water glass or plastic?

Answer 1

I'm guessing the light ray is coming from air. When light passes from air to water, glass or plastic, the light ray "Refracts" meaning it bends towards the medium (The middle). However this is only the case when the second material the light passes through is denser than the original. In your case, air AND vacuum are less dense, infact they are the most dense with a density level of 1. Something like water on the other hand has a density of 1.33 meaning the ray of light that travels from air to water will bend towards the medium.

Lets take another example using one of the material stated in the question, I will continue using water as an example and... Crown glass. Remember water's density level is 1.33 and crown glass has a density level of 1.52. Lets say the light ray travels through water first this time which is known as incident ray and will pass into crown glass. Because crown glass is more dense than water, the ray will bend towards the medium. Ok now lets flip the question around, if the light ray passed through the crown glass first then refracted into water, the complete opposite would now happen; because crown glass is more and water is less dense, the ray this time will bend AWAY from the medium.

Answer 2

Its makes it contribute