Question

A concave lens of focal length 15 cm from an image 10cm from the lens calculate the distance of the object from the lens

Answer 1

★★Question:-

A concave lens of focal length 15 cm from an image 10cm from the lens calculate the distance of the object from the lens.

★★Given:-

focal length (F)=-15 cm after sign conventions

Image distance(V)=-10cm

Object distance(U)=?

★★Answer:-

By using formula,

$\sf\:⇢\dfrac{1}{v}-\dfrac{1}{u}=\dfrac{1}{f}$

$\sf\:⇢\dfrac{1}{-10}-\dfrac{1}{u}=\dfrac{1}{-15}$

$\sf\:⇢\dfrac{1}{u}=-\dfrac{1}{10}+\dfrac{1}{15}$

$\sf\:⇢\dfrac{-3+2}{30}=-\dfrac{1}{30}$

$⇢$$\sf\:\boxed{\boxed{{U=-30cm}}}$

Answer 2

Explanation:

$\frac{1}{v} + \frac{1}{u} = \frac{1}{f} \\ \frac{1}{10} + \frac{1}{u} = \frac{1}{15} \\ \frac{1}{u}= \frac{1}{15} - \frac{1}{10} \\ \frac{1}{u} = \frac{10 - 15}{150} \\ \frac{1}{u} = \frac{ - 5}{150} \\ \frac{1}{u} = \frac{ - 1}{30 } \\ u = - 30$

Hope it helps you