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AP EAMCET · PHYSICS · Ray Optics

When an object is placed infront of a convex mirror at a distance ' \(u\) ' from the pole of the mirror such that the size of the image is ' \(n\) ' times that of the object, then the object distance ' \(u\) ' \(=\)

  1. A \(\frac{\mathrm{f}}{\mathrm{n}^2}-\mathrm{nf}\)
  2. B \(\mathrm{nf}-\frac{\mathrm{f}}{\mathrm{n}}\)
  3. C \(\mathrm{f}-\frac{\mathrm{f}}{\mathrm{n}}\)
  4. D \(\mathrm{f}+\frac{\mathrm{f}}{\mathrm{n}^2}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(\mathrm{f}-\frac{\mathrm{f}}{\mathrm{n}}\)

Step-by-step Solution

Detailed explanation

\(m = -\frac{v}{u}\) \(n = -\frac{v}{u} \Rightarrow v = -nu\) \(\frac{1}{f} = \frac{1}{v} + \frac{1}{u}\) \(\frac{1}{f} = \frac{1}{-nu} + \frac{1}{u}\) \(\frac{1}{f} = \frac{1}{u} \left( 1 - \frac{1}{n} \right) = \frac{1}{u} \left( \frac{n-1}{n} \right)\)…