Question

The image of an object, formed by a plano-convex lens at a distance of 8m behind the lens, is real and is one third the size of the object. The wavelength of light inside the lens is 2/3 times the wavelength in free space. The radius of the curved surface of the lens is 

(a) 1 m

(b) 6 m

(c) 5 m

(d) 3 m

Answer 1

Correct option is d) 3m 

Explaination:: 

\(\mu ={\lambda_0\over \lambda_m}={3\over2}\) 

\({1\over f}={(\mu-1)\over R}={1\over 2R}\) 

\({1\over f}={1\over V}-{1\over u}\) 

\({1\over8}-({1\over24})={1\over2R}\) 

\({3+1\over24}={1\over2R}\)

Comments

R=3
 hence , option d) is correct