Verified Solution • 2025–26 Session moderate

QJEEM20Ph8d43: JEE Main 2020 Physics - Class 12 JEEM20Ph8d43 Solution: An object is gradually moving away from the focal point of a…

An object is gradually moving away from the focal point of a concave mirror along the axis of the mirror. The graphical representation of the magnitude of linear magnification (m) versus distance of the object from the mirror (x) is correctly given by :
(Graphs are drawn schematically and are not to scale)

Multiple Choice Options

  • A https://ik.imagekit.io/novatra/photos/960af4a59da9bba178f46df92bee141a79cf87aa01bba901a0a2962873afea40.webp
  • B https://ik.imagekit.io/novatra/photos/9abff38c01eaf2f732a8de0c77f473f56c51a2a5b52c573b3376f5393bd35171.webp
  • C https://ik.imagekit.io/novatra/photos/39c49362c80e3c2e971702675db5c8fe90f39ac667876e6d86feaa0e4c694502.webp
  • D https://ik.imagekit.io/novatra/photos/2c9cc1d1d4f3f6fc426b2f47339bc8332d621806c2680cacc4eb7ee2955c7e20.webp

Step-by-Step Verified Solution

1v+1u=1f{1 \over v} + {1 \over u} = {1 \over f}

⇒\Rightarrow 1v=1f−1u{1 \over v} = {1 \over f} - {1 \over u} = u−fuf{{u - f} \over {uf}}

⇒\Rightarrow v = ufu−f{{uf} \over {u - f}}

m = - vu{v \over u} = ff−u{f \over {f - u}}

as u approaches f, m approaches infinity

And at u = 2f, m = –1 or |m| = 1

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