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JEE Main 4-April-2025 Paper - Shift 1 — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEEJEE Main 4-April-2025 Paper - Shift 14 Marks
MCQ
When an object is placed 40 cm away from a spherical mirror an image of magnification $\frac{1}{2}$ is produced. To obtain an image with magnification of $\frac{1}{3}$, the object is to be moved :
  • ✓
    40 cm away from the mirror.
  • B
    80 cm away from the mirror.
  • C
    20 cm towards the mirror.
  • D
    20 cm away from the mirror.
✓

Answer

Correct option: A.
40 cm away from the mirror.
(A) 40 cm away from the mirror.
$m=\frac{1}{2}=\frac{f}{f-u}$
$\frac{1}{2}=\frac{\mathrm{f}}{\mathrm{f}-(-40)}$
$\mathrm{f}+40=2 \mathrm{f} \Rightarrow \mathrm{f}=40 \mathrm{~cm}$
now $\mathrm{m}=\frac{1}{3}=\frac{40}{40-\mathrm{u}}$
$40-\mathrm{u}=120 \Rightarrow \mathrm{u}=-80$

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