Question

Converging and diverging of light rays is the property for which of the given pairs
A. Concave lens and Plane mirror respectively
B. Convex lens and Plane mirror respectively
C. Concave lens and convex lens respectively
D. Convex lens and concave lens respectively

Answer 1

Hint: A concave lens is a lens that possesses at least one surface that curves inwards. It spreads out light rays that have been refracted through it. Whereas a convex lens is a lens that converges the incident rays towards the principal axis after refraction through a point called focus, since it converges all the ray at one point.

Complete answer:
If both sides of the lens curve outward, it is called a converging lens, and it will bend light from distant objects inwards toward a single point, called the focal point(F). A ray entering a converging lens through its focal point exits parallel to its axis. If both sides of the lens curve inward, it is called a diverging lens, and light from distant objects will bend outwards. A ray that enters a diverging lens by heading toward the focal point on the opposite side exits parallel to the axis.

Thus, a convex lens is a converging lens because it converges a parallel beam of light rays passing through it at its focus and concave lens is a diverging lens because it diverges the parallel beam of rays passing through it.

Hence the correct option is D.

Note: A ray passing through the centre of either a converging or a diverging lens does not change direction. Light travels more slowly inside a lens than the air and the lenses can actually steer light to the direction we want. The curvature of a lens can make different rays of a light beam refract through different angles. Also note that the diverging rays can be traced backwards until they intersect at a point.