Question

if magnification of concave lens 1/4 and focal length is 15cm find the image distance and object distance​

Answer 1

$\boxed{\sf{ m = \dfrac{h_i}{h_o} = \dfrac{v}{u}}}$

$\dfrac{v}{u} = \dfrac{1}{4}$

$\: u = 4v$

$\boxed {\sf{ \dfrac{1}{f} = \dfrac{1}{v} - \frac{1}{u}} }$

$\dfrac{1}{15} = \dfrac{1}{v} - \dfrac{1}{4v}$

$\dfrac{1}{15} = \dfrac{4 - 1}{4v}$

$\dfrac{1}{15} = \dfrac{3}{4v}$

$4v = 15 \times 3$

$4v = 45$

$\boxed{ \sf{u = 45}}$

$v = \dfrac{45}{4}$

$\boxed {\sf {v = 11.25 \: cm}}$