Question

u=40,v=15,f=? calculate the missing value of convex lens​

Answer 1

Answer:

$\frac{1}{v}-\frac{1}{u}=\frac{1}{f} \\\frac{1}{15}-\frac{1}{40}=\frac{1}{f} \\\frac{1}{f}=\frac{25}{600}\\\frac{1}{f} = \frac{1}{24}\\ f = 24$

Answer 2

Here's your answer,hope it would be helpful