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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: A single lens produces a coloured image of an object illuminated by white light.
Reason: The refractive index of the material of lens is different for different wavelengths of light.
✓

Answer

  1. Both A and R are true and R is the correct explanation of A.
Explanation:
Due to the variation of the refractive index of the material of the lens, the focal length also varies accordingly. Now as white tight is composed of different colours of light, each colour will produce its own image based on the focal length for that colour. This particular phenomenon for a single lens is known as chromatic aberration.

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