What is wavefront?

Consider a point at the focal point of a convergent lens. Another convergent lens of short focal length is placed on the other side. What is the wavefronts emerging from the final image?

Is it correct to say that diffraction is interference between different parts of the same wavefront?

What is meant by a wavefront?What is the shape of the wavefront of a beam of parallel rays?

What is the shape of wavefront orginating fron a line source?

What is the phase difference between two points on a wavefront?

How is a wavefront related to the direction of corresponding rays?

Which one off the following phenomena is not explained by Huygens' construction f wavefront?

The phase difference between any two points situated on the same wavefront is: