Question

Viewing glass of a fish aquarium is of plane convex lens type with radius of curvature $R=30cm$. and refractive index 1.5, If the fish is at 20 cm from glass in water of refractive index 1.2, distance of fish for observer from glass in cm will be (neglect thickness of glass) .

Answer 1

Distance of fish from glass due to refraction from flat surface is $\Rightarrow \frac{{\mu }_2}{{\mu }_1}=\frac{I_d}{O_d}\Rightarrow \frac{1.5}{1.2}=\frac{V_1}{20}$

$V_1=\frac{15\times 20}{12}=25$ cm
By refraction from curved surface
$\frac{{\mu }_2}{V_f}-\frac{{\mu }_1}{V_1}=\frac{{\mu }_2-{\mu }_1}{R}\Rightarrow \frac{1}{V_f}-\frac{1.5}{-25}=\frac{1-1.5}{-30}$
$V_f=23.08$