Question

Find the positions of the principal planes, the focal and nodal points of a thin biconvex symmetric glass lens with curvature radius of its surfaces equal to R = 7.50 cm. There is air on one side of the lens and water on the other.

Answer 1

The primary and secondary focal length of a thick lens are given as,

where Φ is the lens power n , n' and n" are the refractive indices of first medium, lens material and the second medium beyond the lens. Φ₁ and Φ₂ are the powers of first and second spherical surface of the lens.

Since the distance between the primary principal point and primary nodal point is given as,