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Two coherent monochromatic… (Class 12 Physics 2023, Q22)

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PhysicsCBSE Class 12 · Board exam 2023, set 55/1/1 · 2 marks · Very short answer

CBSE Class 12 Physics 2023: question 22

Set in the CBSE Class 12 board exam of 2023, paper 55/1/1, section B, question 22, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q22 · 2 marks · Very short answerWave Optics

Two coherent monochromatic light beams of intensities I and 4I superpose each other. Find the ratio of maximum and minimum intensities in the resulting beam.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 55/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Intensity is proportional to the square of amplitude.

Hint 2

Maximum intensity occurs when amplitudes add, minimum when they subtract.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Intensity (amplitude):

    ½ mark

  2. and

    ½ mark

  3. ½ mark

  4. , i.e. 9 : 1

    ½ mark

Answer:

Where the marks are

  • Amplitude ratio from intensity ratio (½ mark)
  • Writes , (½ mark)
  • Substitution (½ mark)
  • Result 9 : 1 (½ mark)

Revise the chapter

  • Chapter: Wave Optics (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Wave Optics, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 55/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.