How many internal reflections of light take place in the formation of primary rainbow?

CONCEPT:

• Dispersion of light: The phenomenon in which a white light ray when falls on a prism get separated into its component colors is called dispersion of light.
• Primary rainbow: Primary rainbow is the result of One Total internal reflection and two refractions from the suspended raindrop.
  • Violet color forms on the inner edge and red color on the outer edge. Angles subtended with the direction of the sun are 42˚ (red) and 40˚ (violet) above the horizon.
  • The primary rainbow is a result of a three-step process, that is, refraction, reflection, and refraction.

• Secondary Rainbow: Secondary rainbow is the result of two total internal reflections (TIRs) and two refractions from the suspended raindrop.
  • In this rainbow red color appears on the inner edge while violet color appears on the outer edge which is reverse of that of the primary rainbow.
  • This is because of additional reflection which causes a 180˚ phase shift.

EXPLANATION:

• From the above, it is clear that there is 1 internal reflection of light that is taking place in the formation of the primary rainbow. Hence, option 2 is correct.