Question

Two thin symmetrical lenses of different nature have equal radii of curvature of all faces R = 20 cm. The lenses are put close together and immersed in water. The focal length of the system is 24 cm. The difference between refractive indices of the lenses is $\left(\frac{5}{n}\right)$. Find n. The refractive index of water is $\frac{4}{3}$. ___

Answer 1

$\because \because \frac{1}{F}=\frac{1}{f_1}+\frac{1}{f_2}\Rightarrow \frac{1}{24}=[(\frac{{\mu }_1}{\frac{4}{3}}-1)(\frac{1}{20}+\frac{1}{20})+\left(\frac{{\mu }_2}{\frac{4}{3}}\right)(\frac{1}{-20}-\frac{1}{20})]\Rightarrow ({\mu }_1-{\mu }_2)=\left(\frac{5}{9}\right)$