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?

**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**

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