Question

a convex lens of focal length 10 centimetre is placed at a distance of 12 cm from a wall how far from the lens should an object be placed so as to form its real image on the wall ​

Answer 1

Answer: I don't think you can form real image using convex lens..... Only virtual image.....

Explanation:

Answer 2

Solution

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ for \: covex \: lens \: v = + 12cm \: f = 10 \: cm \\ therefore..... \\ \frac{1}{12} - \frac{1}{u} = \frac{1}{10} = > \frac{1}{u} = \frac{1}{12} - \frac{1}{10} \\ = > u = - 60 \: cm$

the object should be placed in the opposite side of the wall .....at a distance of 60 cm