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Q3 (CAPF/2017) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Geometrical optics Answer Verified

Statement I : Occasionally we see two rainbows together, the primary rainbow with another less intense secondary rainbow about 10 degrees away Statement I : The secondary rainbow appears due to refraction after a reflection of sunlight from the water droplets

Result
Your answer:  ·  Correct: C
Explanation

Statement I is true as a secondary rainbow is often observed approximately 10 degrees outside the primary rainbow. The primary rainbow is centered at an angle of about 42°, while the secondary rainbow is centered at approximately 51° to 54° [1]. Statement II is false because the secondary rainbow is specifically formed by two internal reflections within the water droplet, followed by refraction as the light exits [2]. While the primary rainbow involves one internal reflection, the secondary rainbow requires two, which results in its lower intensity and reversed color sequence. The provided text confirms that rainbows are caused by dispersion, refraction, and internal reflection of sunlight by water droplets [2]. Since the secondary rainbow's defining characteristic is the double internal reflection rather than just 'refraction after a reflection', Statement II is technically incomplete or inaccurate in its simplified description of the physical mechanism.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 10: The Human Eye and the Colourful World > Activity 10.2 > p. 167
  2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 24: Hydrological Cycle (Water Cycle) > Explanation: > p. 335
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