CBSE 2022 · Region 1 · Set 1 · Q5 · 3 marks
A point source in air is kept $\displaystyle 24$ cm in front of a concave spherical glass surface $\displaystyle \left({ }_{\mathrm{a}} \mu_{\mathrm{g}}=1.5\right)$ and radius of curvature $\displaystyle 60$ cm. Find the nature of the image formed and its distance from the point source.
Marking-scheme solution
Relation for concave spherical surface
$$
\frac{\mu_{1}}{-u}+\frac{\mu_{2}}{v}=\frac{\mu_{2}-\mu_{1}}{R}$\displaystyle \frac{1}{-u}+\frac{\mu}{\mathrm{v}}=\frac{\mu-1}{R}$\frac{1}{-(-24)}+\frac{1 \cdot 5}{v}=\frac{1 \cdot 5-1}{-60}$\displaystyle \therefore \mathrm{v}=-30 \mathrm{~cm}$
Distance of image from point source $\displaystyle =-24-(-30)=6 \mathrm{~cm}$
Nature of image = Virtual image
Ray Optics and Optical InstrumentsRefraction at Spherical Surfaces and by LensesApplyshort_answermedium
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CBSE Class 12 Physics past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.