Question

I am a lensmaker responsible for creating a Schott N-BK7 glass lens with a nominal thickness of 10mm, and a front surface radius of curvature ground to +75mm. To what radius of curvature should I grind the back surface to get a 105mm infinite image focal length? State all assumptions and sketch what the lens would look like.

Answer 1

For this u have to use the lens maker's formula , which given by

Here f= focal length , R1 = radius of curvature of first face , R2= radius of curvature of second face , μ = refrective index of material you used for making a glass.

In your case,

R1= 75 mm

f= 105 mm

μ=1.5168

Put these value in above lens maker's formula we get

1/R2 =[1/R1 - 1/f(μ-1)] =1/75 -1/54.268

R2 =- 196.31 mm

Which is the required radius of curvature of other side of lens.

It is look like as shown in fig. below