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Ray Optics and Optical Instruments — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsRay Optics and Optical Instruments1 Mark
Question
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is not the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion: The minimum distance between an object and its real image formed by a convex lens is 2f.
Reason: The distance between an object and its real image is minimum when its magnification is two.
✓

Answer

  1. A is false and R is also false.
Explanation:
The distance between the object and its real image is minimum when magnification is I. We know that the magnification of convex lens is given by $\text{m}=-\frac{\text{v}}{\text{u}}$ for m = 1, v = -u.
Now from lens formula, v = u = 2f
Hence, minimum distance v + u = 4f.

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