Rays and Wavefronts

Q.

The focal length of a convex lens is always positive.

1. True
2. False

Q. A plane wavefront hits convex lens as shown in figure. Which graph represent refracted wavefront from lens.

1. 
2. 
3. 
4. 

Q. Define the term wave front. State Huygen's principle. Consider a plane wave front incident on a thin convex lens. Draw a proper diagram to show how the incident wave front traverses through the lens and after refraction focuses on the focal point of the lens, giving the shape of the emergent wave front.

Q. Which of these look(s) like a possible setup to get cylindrical wavefronts?

1. 
2. 
3. 
4. None of these.

Q. A plane wavefront hits convex lens as shown in figure. Which graph represent refracted wavefront from lens.

1. 
2. 
3. 
4. 

Q. geometrical shape of a wavefrontwhen plane wave passes through a convex lens.