Question

A lens produces An erect image of size 6 mm when an object of size 3 mm is placed at 20 cm from its optical centre

Answer 1

Given:-

$u = - 20mm \\ h = 3mm \\ {h}^{..} = 6mm \\ v = ?$

Here h`= 6mm (in above 3rd line ,I used h.. as height of image)

Now,

$m = \frac{ {h}^{..} }{h} = \frac{v}{u}$