Question

que) A real image 2/3 of size of an object is formed by a convex lens when the object is at a distance of 12 cm from it find the focal length of the lens​

Answer 1

$\mathfrak{\bf{\underline{\underline{GIVEN \ :}}}}$

$ㅤㅤㅤㅤㅤm = \frac{2}{3} \\ ㅤㅤㅤㅤㅤㅤㅤv = + 12cm$

$\mathfrak{\bf{\underline{\underline{SOLUTION \ :}}}}$

$\implies \: m = \frac{v}{u} \\ \: \\ \implies m = - \frac{2}{3} \\ \: \\ \implies m = 12 u \\ \: \: \: \\ \: \: \implies- 2u = 36 \\ \\ \: \: \: \: \: \: \: \implies \: u = - 18 \: cm$

BY LENS FORMULA :-

$\impliesㅤㅤㅤㅤㅤㅤㅤ \frac{1}{f} = \frac{1}{v} - \frac{1}{u}$

$\implies \: ㅤㅤㅤㅤㅤㅤ \: \frac{1}{f} = \frac{1}{12} - \frac{1}{ (-18) }$

$\implies \: ㅤㅤㅤㅤㅤㅤ \frac{1}{f} = \frac{1}{12} + \frac{1}{18}$

$\implies \: ㅤㅤㅤㅤㅤㅤ\frac{1}{f} = \frac{3}{36} + \frac{2}{36}$

$\implies \: ㅤㅤㅤㅤㅤㅤ\frac{1}{f} = \frac{5}{36}$

$\implies \:ㅤㅤㅤㅤㅤㅤㅤ f = \frac{36}{5}$

$\implies \:ㅤㅤㅤㅤㅤ \boxed{\boxed{ f \approx 7.2 \: cm}}$

ㅤㅤㅤㅤㅤ

ㅤㅤㅤㅤㅤhєncє, thє fσcαl lєnght íѕ 7.2 cm

ㅤ

$\mathfrak{\bf{\underline{\underline{EXTRA \ INFORMATION \ :-}}}}$

ㅤ

ㅤ$\implies$ тhє ímαgє fσrmєd íѕ rєαl. ( cσnvєх lєnѕ fσrmѕ dímíníѕhєd rєαl ímαgє. )

Answer 2

Answer:

How you can do upon in mobile please tell me