Question

Explain the lens with its types and working.

Answer 1

About lens:

1. A lens is a transparent piece of glass with one or more curved sides.
2. A lens works by refraction i.e, bending of a ray of light as it passes through the lens.
3. This implies that the rays seem to be originating from a point closer or further than the actual position of the body. The object can also appear bigger or smaller than the actual size.
4. Mainly lenses can be classified as concave lens and convex lens.

Convex lens:

1. The above image shows the image formation for different positions of object when placed near a convex lens
2. When object is at infinity, image is obtained at focus on the other side.
3. When object lies at a distance more than twice the focal length($2F$), image is formed between $F$ and $2F$ on the other side of the lens,
4. When object lies at twice the focal length distance, image is formed at the same distance on the other side.
5. When object is placed between $F$ and $2F$, image is formed beyond $2F$ on the other side.
6. When object is placed at $F$, image is formed at infinity.
7. When object is at a distance lesser than focal length, a virtual image is obtained on the same side.

Concave lens:

1. Unlike convex lens, concave lens has only two positions of images.
2. When object is at infinity, virtual image is obtained at focus.
3. For all other positions of object, virtual image is obtained at a distance lesser than focal length.