Question 1 What is a lens?

Question 2 How many type of lens are them?

Question 3 What is a convex lens?

Question 4 What is a concave lens?

Question 5 Draw Bi-convex, plane-convex and concavo-convex lens?

Question 6 Draw Bi-concave, plane-concave and convexo-concave lens?

Contents

**Refraction by Spherical Lenses**

Lens is a transparent medium bounded by two refracting surfaces.

**Types of lenses**

**(1) Convex or converging**

(2) Concave or diverging

**Convex Lens**

A lens having both spherical surface or one spherical and other plane surface.

It is thick in the middle and thin at the edges.

They are of 3 types:

**(a) Bi-convex**

**(b) Plane-convex**

**(c) Concavo-convex**

**Concave lens**

**(a) Bi-concave**

**(b) Plane-concave**

**(c) Convexo-Concave**