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

Explanation

All are correct

• A rainbow is a natural optical phenomenon resulting from the interaction of sunlight with water droplets in the atmosphere. It is caused by refraction, internal reflection, and dispersion of light within the droplets, producing a spectrum of collars in the form of a circular arc.
• The rainbow consists of seven colours arranged in the following order: red (outermost), orange, yellow, green, blue, indigo and violet (innermost).
• Formation of a Rainbow:
  • Refraction: When sunlight enters a water droplet, it slows down and bends due to a change in medium (air to water).
  • Dispersion: The light separates into its constituent colours (spectrum) because each colour has a different wavelength and refracts at a slightly different angle.
  • Internal Reflection: The light reflects off the inside surface of the water droplet.
  • Refraction Again: As the light exits the droplet, it refracts again, bending further and enhancing the separation of colours.

Answer: (d) 1, 2 and 3; Difficulty Level: Easy