You can see that the sunlight that reaches the Earth travels at different wavelengths. On a sunny day, put a full glass of water (a real glass glass) in the sunshine on your windowsill. Look where the sunshine goes through the water, and you should see rainbows on the floor or walls.
Those rainbows happen when the waterbends the waves of sunlight going through it. The light coming from the sun looks white because it is a mixture of all wavelengths of light. When the light goes through the water, the shorter wavelengths get bent more than the longer wavelengths do, so you end up with the short wavelengths hitting the wall or the table at a different place from the longer wavelengths: that’s what makes a rainbow.