Question

calculate the focal length of a biconvex lens in the radii of the surfaces are 50 cm and 20 cm and the index refraction of the lens glass = 1.2​

Answer 1

Explanation:

Refractive index of glass μ=1.5

Given : R

1

=20 cm R

2

=−30 cm

Using lens maker formula :

f

1

=(μ−1)(

R

1

1

−

R

21 )

Or

f1 =(1.5−1)( 201− (−30)1 )

⟹ f=24 cm