A stick partially immersed obliquely under water appears to be bent.Explain,why.

Why does a pencil immersed in water appear bent and short? Explain with the help of a ray diagram?

Why do the oil films on the surface of water appear to be coloured?

A ray of light travelling in air enters obliquely into water. Does the light ray bend towards normal or away from normal? Why?

Why does a block of plastic immersed under water come to the surface of water ?

Why is yellow phosphorus kept under water ?

Occasionally one sees an aircarft in the sky shortly after suset o shortly before sunrise and is surprised to see that it appears to be very bright,more like a star or planet than like an aircraft as seen in daylight.Explain,why.