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JEE Main 20254 AprilEvening Shift
Exam
JEE Main
Year
2025
Date
4 April
Shift
Evening Shift
Subject
Physics
Chapter
Ray Optics

JEE Main 2025 · 4 April · Evening Shift · Physics · Ray Optics

A finite size object is placed normal to the principal axis at a...

A finite size object is placed normal to the principal axis at a distance of 30 cm from a convex mirror of focal length 30 cm. A plane mirror is now placed in such a way that the image produced by both the mirrors coincide with each other. The distance between the two mirrors is :A finite size object is placed normal to the principal axis at a distance of 30 cm from a convex mirror of focal length

Options

  1. A45 cm
  2. B7.5 cm
  3. C22.5 cm
  4. D15 cm

Correct answer

B. 7.5 cm

Step-by-step solution

A finite size object is placed normal to the principal axis at a distance of 30 cm from a convex mirror of focal length
For Convex mirror
<br/>1v+1u=1f1v−130=1301v=230=115⇒v=15 cm<br/>\begin{aligned}<br/>& \frac{1}{\mathrm{v}}+\frac{1}{\mathrm{u}}=\frac{1}{\mathrm{f}} \\ & \frac{1}{\mathrm{v}}-\frac{1}{30}=\frac{1}{30} \\ & \frac{1}{\mathrm{v}}=\frac{2}{30}=\frac{1}{15} \Rightarrow \mathrm{v}=15 \mathrm{~cm}<br/>\end{aligned}
Image formed by convex mirror is at 45 cm from object so plane mirror should be placed midway at 22.5 cm from object so that both of their images may coinside,
Therefore distance between both mirrors
=30−22.5=7.5 cm=30-22.5=7.5 \mathrm{~cm}
Correct Answer : Option 2
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