Question

the focal length for a convex lens is 10 centimetre if object is kept at a distance of 4 cm which is the image distance.​

Answer 1

${\huge{\bold{\underline{\mathfrak{\blue{AnSwer}}}}}}$

Given:-

•Focal length(f) = 10cm

•Object distance(u) = -4cm

To find :-

•Image distance(v)

Solution:-

$\large\red{\boxed{\sf\frac{1}{f} = \frac{1}{v}+ \frac{1}{u} }}$

$\large\sf\leadsto\frac{1}{10}= \frac{1}{v}+ \frac{1}{-4} \\ \\ \large\sf\leadsto\frac{1}{v} = \frac{1}{-4} - \frac{1}{10} \\ \\ \large\sf\leadsto\frac{1}{v} = \frac{-5-2}{20} \\ \\ \large\sf\leadsto\frac{1}{v} = \frac{-7}{20} \\ \\ \large\sf\leadsto\ v = \frac{20}{-7} \\ \\ \large\bf\leadsto\ v= -2.85cm$