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| 1. |
Prove R=2f |
| Answer» Consider a ray of light AB, parallel to the principal axis, incident on a spherical mirror at point B. The normal to the surface at point B is CB and CP = CB = R, is the radius of curvature. The ray AB, after reflection from mirror will pass through F (concave mirror) or will appear to diverge from F (convex mirror) and obeys law of reflection, i.e., i = r.If the aperture of the mirror is small, B lies close to P, BF = PFor FC = FP = PFor PC = PF + FC = PF + PFor R = 2 PF = 2for F=R/2or 2F= R\xa0 | |