Question

Find the positions of the principal planes, the focal length and the sign of the optical power of a thick convex-concave glass lens 

(a) whose thickness is equal to d and curvature radii of the surfaces are the same and equal to R; 

(b) whose refractive surfaces are concentric and have the curvature radii R₁ and R, (R₂ > R₁).

Answer 1

(a) The power of the lens is

The principal planes are located on the side of the convex surface at a distance d from each other, with the front principal plane being removed from the con vex surface of the lens by a distance R /(n - 1) .

Both principal planes pass through the common centre of curvature of the surface of the lens.