Question

A spherical surface of radius of curvature 10 cm separates two media X and Y of refractive indices 3/2 and 4/3 respectively. Centre of the spherical surface lies in denser medium. An object is placed in medium X. For image to be real, the object distance must be

• A. greater than 90 cm
• B. less than 90 cm
• C. greater than 80 cm
• D. less than 80 cm

Answer 1

Answer: (C)

greater than 80 cm

$\frac{{\mu }_2}{v}-\frac{{\mu }_1}{u}=\frac{{\mu }_2-{\mu }_1}{R}$

$\frac{1.5}{v}+\frac{4}{3X}=\frac{1}{60}$

for a real image $v>0$

=> $\frac{1}{60}-\frac{4}{3X}>0$

$X>80$

option $C$ is correct