Question

A small object is 2 cm below the concave meniscus of water in a test tube.The radius of the meniscus is 5mm and $\mu =4/3$ for water. Find the nature and position of the image.

Answer 1

$\frac{\mu }{v}-\frac{1}{u}=\frac{(\mu -1)}{R}$

So $\mu =\frac{4}{3}$

R = 5mm

u = -20mm

So

$\frac{\frac{4}{3}}{v}=\frac{1}{-20}=\frac{1}{3\times 5mm}$

$\frac{4}{3v}=\frac{1}{15}-\frac{1}{20}=\frac{5}{15\times 20}=\frac{1}{60}$

$v=80cm$

hence a real image is observed, magnified at a distance of 80cm.