Question

Things always look small on viewing through a lens. What kind of lens is it ?
A. Concave lens
B. Convex lens
C. Bipolar lens
D. Crystalline lens

Answer 1

Hint:A lens is a transmissive optical device that utilises refraction to concentrate or scatter a light beam. A simple lens is made up of a single transparent component, whereas a compound lens is made up of many simple lenses (elements) that are generally aligned along a common axis. Ground and polished or moulded to a particular form, lenses are produced from materials such as glass or plastic.

Complete answer:
Spherical lenses are made by combining two spherical transparent surfaces. There are two types of spherical lenses in general. Convex lenses are made by joining two spherical surfaces that bulge outward, whereas concave lenses are made by joining two spherical surfaces that bend inward.

One of the most fundamental differences between concave and convex lenses is this. Convex lenses are also called converging lenses because the rays converge after passing through them, whereas concave lenses are called diverging lenses because the rays diverge after passing through them.

The borders of a concave lens are thicker than the centre, and the middle is narrower.Because two spherical surfaces bulge inwards, a concave lens is sometimes known as a "biconcave lens." Plano-concave lenses (i.e., lenses that are flat on one side and curved inward on the other) and concave meniscus lenses (i.e., lenses that are curved inward on one side and less strongly curved on the outer side) are examples of concave lenses. We usually obtain erect pictures, reduced images, and virtual images while using a concave lens. If the item is really far away, the pictures created by the lenses will be significantly reduced.

Hence, the correct option A.

Note:The curvature of the two optical surfaces is used to classify lenses. If both surfaces of a lens are convex, it is called biconvex (or double convex, or simply convex). The lens is equiconvex if both surfaces have the same radius of curvature. Biconcave refers to a lens having two concave sides (or just concave). The lens is plano-convex or plano-concave depending on the curvature of the other surface if one of the surfaces is flat. Convex-concave or meniscus lenses have one convex and one concave side. This is the most frequent kind of lens used in corrective lenses.