Question

An object is placed at a distance of 40 cm in front of a convex mirror The image appears 15 cm behind the mirror.find focal length

Answer 1

$\large{\textbf{\underline{Focal length = 24 cm }}}$

$\huge{\textbf{\underline{As per Question:-}}}$

Object distance ( u ) = -40 cm

Image distance ( v ) = 15 cm

$\huge{\textbf{\underline{To find :-}}}$

$\large{\textbf{Focal length of convex mirror}}$

$\huge{\textbf{\underline{Using Mirror Formula:-}}}$

$\large{\boxed{\dfrac{1}{f}= \dfrac{1}{u} + \dfrac{1}{v}}}$

$\mathsf{\dfrac{1}{f}= \dfrac{1}{(-40)}+ \dfrac{1}{15}}$

$\mathsf{\dfrac{1}{f}= \dfrac{-1}{40}+\dfrac{1}{15}}$

$\mathsf{ \dfrac{1}{f}= \dfrac{-3+ 8}{120}}$

$\mathsf{\dfrac{1}{f}= \dfrac{5}{120}}$

$\mathsf{\dfrac{1}{f}= \dfrac{1}{24}}$

$\therefore \textbf{ f = 24 cm }$