Question

A convex lens is made up of three different materials as shown in the figure. Then the number of images it forms will be

A. Three images are formed at the same place.
B. Three images are formed at different places.
C. Only one image is formed.
D. No image is formed.

Answer 1

Hint: Three refractive indexes give three types of focal lengths. Different focal lengths indicate possibilities for several images. Changes in refractive index affect the size and position of the image formation.

Complete step by step answer:
The given convex lens is made up of three different materials and these materials have different refractive index. So, the given lens has three different focal lengths. Thus, it forms three images on the screen at three different places. Hence, the correct option is B.
Additional information: A lens is an optical system with two refractive surfaces and which have a common axis. When each surface forms a part of the sphere, then the lens is called a spherical lens. Converging lens or convex lens and diverging lens or concave lens are two categories of spherical lenses.
Converging lens: it’s a positive lens since their focal lengths are positive. When a beam of rays parallel to the axis passes through the convex lens, the rays converge to a focal point and form a real image at that point. We can identify convex lenses easily because their centre will be thicker than its edges. It can produce virtual or real images.
Diverging lens: It’s a negative lens since their focal lengths are negative. The parallel beam of rays incident on the concave lens diverges after refraction. Any lens that is thicker at the edges than its centre is known as a concave lens. It will produce virtual images.

Note: Three images form at different places since the images are forming at different focal lengths. Studies are showing that if the refractive index is increasing, then focal points will be closer to the lens and vice versa.