Easy MCQ +4 / -1 PYQ · JEE Mains 2021

An object is placed beyond the centre of curvature C of the given concave mirror. If the distance of the object is d1 from C and the distance of the image formed is d2 from C, the radius of curvature of this mirror is :

  1. A ${{2{d_1}{d_2}} \over {{d_1} - {d_2}}}$ Correct answer
  2. B ${{2{d_1}{d_2}} \over {{d_1} + {d_2}}}$
  3. C ${{{d_1}{d_2}} \over {{d_1} + {d_2}}}$
  4. D ${{{d_1}{d_2}} \over {{d_1} - {d_2}}}$

Solution

Using Newton's formula<br><br>$(f + {d_1})(f - {d_2}) = {f^2}$<br><br>${f^2} + f{d_1} - f{d_2} - {d_1}{d_2} = {f^2}$<br><br>$f = {{{d_1}{d_2}} \over {{d_1} - {d_2}}}$<br><br>$\therefore$ $R = {{2{d_1}{d_2}} \over {{d_1} - {d_2}}}$

About this question

Subject: Physics · Chapter: Optics · Topic: Reflection and Mirrors

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