What is ray of light w.r.t. wavefront ?

What is wavefront ? What is the shape of the wavefront at a point far away from the source of light?

What is the shape of the wavefront in each of the following cases : light diverging from a point source

What is the shape of the wavefront on Earth for sunlight?

Define wavefront, wavenormal and a ray of light. What are the different types of wavefronts? How are they produced ?

What is the shape of a wavefront emitted by a light source in the form of a narrow slit ?

The speed of light in water and diamond is 2.25 xx 10^(8) m//s and 1.25 xx 10^(8) m//s respectively. What is the refractive index of : diamond w.r.t. water?

The speed of light in water and diamond is 2.25 xx 10^(8) m//s and 1.25 xx 10^(8) m//s respectively. What is the refractive index of : water w.r.t. diamond?

A ray of light is incident on a glass plate of refractive index 1.5. The angle between the reflected and refracted rays is 90^@ . What is the ratio of wavelength of reflected t refracted rays ?