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MCQ practice · SSC Physics Board questions · Chapter 8: Reflection of Light

Mymensingh Board 2021

In the figure-

  1. i. the image of the object AB will be virtual and upright
  2. ii. if the object AB is 2 cm long the image will be 6 cm long
  3. iii. if AB is moved 16 cm to the left the magnification will be 1

Think it through first, then pick an option.

  1. a i and ii
  2. b i and iii
  3. c ii and iii
  4. d i, ii and iii
Answer and explanation

Correct answer: d i, ii and iii

In the figure C to F is 12 cm and CF = f, so f = 12 cm. A is 8 cm from the mirror, inside the focus: i is true (virtual, upright). 1/v = 1/12 − 1/8 = −1/24, v = −24 cm, m = 24 ÷ 8 = 3: 2 cm gives 6 cm, ii is true. Moving 16 cm to the left makes u = 24 cm = 2f (at C): m = 1, iii is true.

Why the other options are wrong

  • a i and ii: This is not the answer: i and ii are true, but iii is true as well: with the object at 2f = 24 cm, m = 1. So all three are correct.
  • b i and iii: This is not the answer: i and iii are true, but ii is true as well: m = 3, so a 2 cm object gives a 6 cm image. So all three are correct.
  • c ii and iii: This is not the answer: ii and iii are true, but i is true as well: the object is inside the focus, so the image is virtual and upright. So all three are correct.

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