Question 5(i)A convex lens of focal length 10 cm is placed at a distance of 60 cm from a screen. How far from the lens should an object be placed so as to obtain a real image on the screen?

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Accepted Answer

Given, focal length = 10 cmImage distance (v) = 60 cmObject distance (u) = ?From lens formula —1v−1u=1f\dfrac{1}{v} - \dfrac{1}{u} = \dfrac{1}{f} \[1em]v1​−u1​=f1​Substituting the values in the formula we get,160−1u=110⇒160−110=1u⇒1−660=1u⇒−560=1u⇒1u=−112⇒u=−12\dfrac{1}{60} - \dfrac{1}{\text{u}} = \dfrac{1}{10} \[1em] \Rightarrow \dfrac{1}{60} - \dfrac{1}{10} = \dfrac{1}{\text{u}} \[1em] \Rightarrow \dfrac{1 - 6}{60} = \dfrac{1}{\text{u}} \[1em] \Rightarrow \dfrac{-5}{60} = \dfrac{1}{\text{u}} \[1em] \Rightarrow \dfrac{1}{\text{u}} = \dfrac{-1}{12} \[1em] \Rightarrow u = -12601​−u1​=101​⇒601​−101​=u1​⇒601−6​=u1​⇒60−5​=u1​⇒u1​=12−1​⇒u=−12∴ The object should be placed at a distance of 12 cm in front of the lens.

Solved 2023 Question Paper ICSE Class 10 Physics — Question 4

Question 5(i)