Question

Define a wavefront. An incident plane wave falls on a convex lens and gets refracted through it. Draw a diagram to show the incident and re fracted wavefront.

Hint:

Wavefronts represent the phase surfaces of a wave, and the shape of the wavefront changes depending on the medium or the lens used to refract the wave.

Answer 1

Wavefronts and Refraction via a Convex Lens

A wavefront is defined as the surface of constant phase, or the locus of all points exhibiting the same phase of vibration. Three primary types of wavefronts exist:

• Spherical wavefronts: Generated by a point source.
• Cylindrical wavefronts: Generated by a line source.
• Plane wavefronts: Generated by a distant source.

Refraction of a Plane Wavefront by a Convex Lens:

Upon passing through a convex lens, a plane wavefront undergoes refraction, resulting in a shape modification. Its behavior is as follows:

• The incident wavefront is parallel (linear) to the lens's axis.
• Post-refraction, the wavefront converges and focuses toward the lens's focal point.
• The convergence of the refracted wavefront toward the focal point is dependent on the lens's curvature.

The accompanying diagram illustrates this phenomenon:

Summary:

The incident wavefront is straight and parallel to the axis; subsequent to traversing the convex lens, the refracted wavefront converges on the lens's focal point.