Question

a parallel beam of light incident on a lens seems to emanate from a point on the principal axis is at a distance of 25cm then find the radius of curvature ​

Answer 1

Answer:

Explanation:

R1 = +ve       R2 = -ve

R1 = R2 = R      for equiconvex lens

Since u = ∞  and f is +ve for converging lens

1/f = 1/v- 1/u

1/f = 1/v - 1/∞

1/f = 1/25+1/∞

1/f = ( µ-1 ) ( 1/R1 - 1/R2 )        since µg = 3/2

1/25 = ( 3/2 - 1 ) (1/R -+ 1/R)

1/25 = 1/2×2/R

R = 25 cm.