Draw a diagram showing the refraction of a light ray from water to glass. Label on it the incident ray, the angle of incidence ($i$), and the angle of refraction ($r$).

Explain why a coin placed at the bottom of a vessel appears to be raised when water is poured in the vessel.

Explain why a straight stick partly dipped in water obliquely, appears to be bent at the surface of the water.

Explain why the sun is seen before the sunrise and after the sunset.