Question

What is the question for R=2f answer

Answer 1

The question might be - Prove R=2f

Basically, this formula is use in spherical mirrors where R is Radius and f is focal length

hope this helps u....:-)

Answer 2

Answer:

Radius of curvature of spherical lens is the question

Explanation:

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.    

From the geometry of the figure, if the aperture of the mirror is small, B lies close to P.  

Therefore, BF=PF  

or FC=FP=PF    

or PC=PF+FC

       =PF+PF  

or R=2PF  

or R=2f