Question

find the focal length of a convex lens with produces a virtual image at 10 cm from the lens when an object is placed at 5 cm from the lens ​

Answer 1

Here, the convex lens is forming a virtual image, so while calculating, we are to take all values negative.

u= -5 cm

v= -10cm

f=?

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ - \frac{1}{10} - ( - \frac{1}{5} ) = \frac{1}{f} \\ - \frac{1}{10} + \frac{1}{5} = \frac{1}{f} \\ \frac{ - 1 + 2}{10} = \frac{1}{f} \\ f = 10 \: cm$

Hence, focal length is 10 cm.

Answer 2

Answer:

F=10 cm

Explanation:

Explanation is in the above pic

Hope this answer may help you....