Question 219: Ray Optics

Question

A plano-convex lens (focal length f2, refractive index $$\mu $$2, radius of curvature R) fits exactly into a plano-concave lens (focal length f1, refractive index $$\mu $$1, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be :

Accepted Answer

$${1 \over F} = {1 \over {{f_1}}} + {1 \over {{f_2}}} = {{1 - {\mu _1}} \over R} + {{{\mu _2} - 1} \over R}$$

Answer

f1 + f2

Answer

f1 $$-$$ f2

Answer

$${R \over {{\mu _2} - {\mu _1}}}$$

Answer

$${{2{f_1}{f_2}} \over {{f_1} + {f_2}}}$$

Ray Optics

A plano-convex lens (focal length f2, refractive index $\mu 2, radius of curvature R) fits exactly into a plano-concave lens (focal length f1, refractive index \mu $1, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be :

Choose the correct answer: