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Science · 2023 · 3 marks
CBSE 2023 · Region 4 · Set 1 · Q31
The power of a lens is+4D. Find the focal length of this lens. An object is placed at a distance of $\displaystyle 50$ cm from the optical centre of this lens. State the nature and magnification of the image formed by the lens and also draw a ray diagram to justify your answer.
Marking-scheme solution
Focal length of lens, \(\displaystyle \mathrm{f}(\mathrm{m})=\frac{1}{\mathrm{P}}\)
\[\mathrm{P}=+4 \cdot 0 \mathrm{D}
\]
\[\Rightarrow f=\frac{1}{+4 D}=0.25 m=25 c m
\]
Real and inverted
Magnification \(\displaystyle =-1\)
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CBSE Class 10 Science past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.