Question

Find the power of convex lens which forms a real and inverted image of magnification – ½ of an object placed at a distance of 20 cm from its optical centre.

Hello. Gummie :) ​

Answer 1

Answer:

$given \: magnification \: = - 1 \: and \: object \: distance \: \\ u = - 20cm \\ we \: know \: magnifcation \: m = \frac{ - v}{u} \\ v = mc = ( - 1)( - 20) = 20cm \\ now \: from \: lens \: fomula \: we \: have \: \\ \frac{1}{v} - \frac{1}{u} = \frac{1}{f} \\ \frac{1}{20} - \frac{ - 1}{20} = \frac{1}{f} \\ f = 10cm \\ now \: powerp \frac{1}{f} = \frac{1}{10} = 100$