Rainbows have so many colors because sunlight is actually made of all those colors mixed together! When it shines through tiny raindrops, the water acts like a little prism and spreads out all the hidden colors for us to see. It's like magic!
Heads upThe answer simplifies the concept of light refraction and dispersion, which are the scientific terms for light bending and separating into colors. At this depth, focusing on the 'hidden colors' in sunlight and the 'water separating' them is sufficient. These specific terms can be introduced when the child has a better grasp of light as a wave.
For youRainbows form because sunlight, which appears white, is composed of a spectrum of colors. When sunlight passes through water droplets (like raindrops), the light bends or 'refracts,' separating into its individual color components due to each color bending at a slightly different angle. This phenomenon is why we see a band of colors rather than just white light.