Solved 2024 Specimen Paper ICSE Class 10 Physics — Question 4

(a) Real and inverted image is formed.

(b) Given, focal length = 8 cm

Object distance (u) = -24 cm

Image distance (v) = ?

From lens formula —

$\dfrac{1}{v} - \dfrac{1}{u} = \dfrac{1}{f} \\[1em]$

Substituting the values in the formula we get,

$\dfrac{1}{\text{v}} - \dfrac{1}{-24} = \dfrac{1}{8} \\[1em] \dfrac{1}{\text{v}} + \dfrac{1}{24} = \dfrac{1}{8} \\[1em] \dfrac{1}{\text{v}} = \dfrac{1}{8} - \dfrac{1}{24}\\[1em] \Rightarrow \dfrac{1}{\text{v}} = \dfrac{3 - 1}{24} \\[1em] \Rightarrow \dfrac{1}{\text{v}} = \dfrac{2}{24} \\[1em] \Rightarrow \dfrac{1}{\text{v}} = \dfrac{1}{12} \\[1em] \Rightarrow v = 12$

∴ The image is formed at a distance of 12 cm behind the lens.