Civil Services Prep

Prelims 2013 · Science and Technology · Question 40

Rainbow is produced when sunlight falls on drops of rain. Which of the following physical phenomena are responsible for this?

  1. Dispersion
  2. Refraction
  3. Internal reflection

Select the correct answer using the codes given below:

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1 and 3 only
  4. 1, 2 and 3

Answer

1, 2 and 3

1. Dispersion — Sunlight splits into its constituent colours inside raindrops because different wavelengths deviate by different amounts. Verdict: Correct.

2. Refraction — Light is refracted when it enters the raindrop and again when it emerges. This bending is essential in rainbow formation. Verdict: Correct.

3. Internal reflection — After entering the drop, light undergoes internal reflection before coming out toward the observer. This is a key step in forming the primary rainbow. Verdict: Correct.

Hence, all three phenomena are involved in rainbow formation.

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