Question

Derive lens makers' equation. Why is it
called so? Under which conditions focal
length f and radii of curvature R are
numerically equal for a lens?​

Answer 1

Answer:

Explanation:

n2=n

n1=1

R=R1

u=u

V=v1

n-1/R1=n/v1 -1/u -------(I)

1-n/R2=n-1/-R2=1/v-n/u --------(ii)

Add eqn (I) and (ii)

(n-1) (1/R1-1/R2)=1/v-1/u

For u=infinity v=f

1/f=(n-1)(1/R1 - 1/ R2)

This is lens makers formula .for preparing spectacles , it's necessary to grind the glass for having the desired radii of curvature ...1/f =(n-1)(1/R1 -1/R2) is used to calculate the radii of curvature for the lens . Hence it is called lens makers formula ...

If n=1.5,f=2*R

Answer 2

Answer:Lens makers formula is :

1/f = [ n-1 ] × [ 1/R1-1/R2 ]

Explanation: