Question

An object of 4cm is placed 10cm away from convex
lens of focal length 20 cm. What is the size and
distance of image . Also calculate the magnification
of​

Answer 1

Answer:

$v = - 20cm \\ size \: of \: image = 8cm \\ m = 2$

Explanation:

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ u = - 10cm \\ f = + 20cm \\ \frac{1}{v} - \frac{1}{ - 10} = \frac{1}{20} \\ \frac{1}{v} + \frac{1}{10} = \frac{1}{20} \\ \frac{1}{v} = \frac{1}{20} - \frac{1}{10} \\ v = - 20cm \\ m = \frac{v}{u} = \frac{ - 20}{ - 10} = 2 = \frac{size \: of \: image}{size \: of \: object} = \frac{size \: of \: image}{4} \\ size \: of \: image =8cm$