Refraction by spherical lenses

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