What phenomenon causes a rainbow to appear after rain?

• A. Refraction and reflection of light
• B. Diffraction of light
• C. Absorption of light
• D. Polarization of light

Answer: (A)

The appearance of a rainbow after rain is primarily the result of the refraction and reflection of light within water droplets suspended in the air. When sunlight encounters these droplets, it first refracts, or bends, as it enters the droplet. This bending of light causes it to spread out into its constituent colors, creating a spectrum.

Once inside the droplet, the light reflects off the back surface before exiting through the front. As it exits the droplet, it refracts again, enhancing the separation of colors. This process results in the colorful arc of a rainbow that is visible to an observer, with red on the outer edge and violet on the inner edge.

The other options, such as diffraction, absorption, and polarization, do not play a significant role in the formation of a rainbow. Diffraction involves the bending of light waves around obstacles, while absorption refers to the loss of light energy as it passes through a medium. Polarization involves the orientation of light waves but does not contribute to the color dispersion required for rainbows. Thus, the correct answer emphasizes the importance of light refraction and reflection in creating this beautiful optical phenomenon.