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Science · 2024 · 5 marks
CBSE 2024 · Region 2 · Set 1 · Q36
(a)Upper half of a convex lens is covered with a black paper. Draw a ray diagram to show the formation of image of an object placed at a distance of 2F from such a lens. Mention the position and nature of the image formed. State the observable difference in the image obtained if the lens is uncovered. Give reason to justify your answer.(b)An object is placed at a distance of $\displaystyle 30$ cm from the optical centre of a concave lens of focal length $\displaystyle 15$ cm. Use lens formula to determine the distance of the image from the optical centre of the lens.
(a)
Upper half of a convex lens is covered with a black paper. Draw a ray diagram to show the formation of image of an object placed at a distance of 2F from such a lens. Mention the position and nature of the image formed. State the observable difference in the image obtained if the lens is uncovered. Give reason to justify your answer.
(b)
An object is placed at a distance of $\displaystyle 30$ cm from the optical centre of a concave lens of focal length $\displaystyle 15$ cm. Use lens formula to determine the distance of the image from the optical centre of the lens.
Marking-scheme solution
\[\begin{gathered}
\frac{1}{v}-\frac{1}{u}=\frac{1}{\mathrm{f}} \\
\frac{1}{v}=\frac{1}{\mathrm{f}}+\frac{1}{u} \\
=\frac{1}{-15}+\frac{1}{-30} \\
v=-10 \mathrm{~cm}
\end{gathered}
\]
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CBSE Class 10 Science past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.