Geometrical optics. Photometry. Quantum nature of light > Rectilinear propagation and reflection of light > Problem 13.1.13

Statement

$13.1.13.$ Determine the focal length of a spherical mirror of radius of curvature R.

Solution

Here it was used that h' = 0, no matter what the original h value is. Since the incident height does not change where the ray converges. I would also like to note, that I made a small error, For a light ray travelling at an angle, I wrote sin(β), it is supposed to be tan(β), but we can still use the small angle approximation. So it doesn't change the result.

Answer

[R/2]