How is a rainbow a physical change?

Answer 1

A true change in color is almost always associated with a chemical change.

Here are a few examples of visual changes that are not color changes due to physical change.

Chemical change: When your toast changes from white to brown, the heat of the toaster has caused a chemical change in the outer layer of the toast.

Physical Change: When rain changes to snow, we have the impression that it appears different. Water appears transparent and snow appears white, but the difference is really a difference of how light is scatters from snow. (A white color normally means diffuse reflection.)

Chemical Change: Photochromic eyeglasses are normal transparent glasses which darken when exposed to sunlight. This is an example of reversible chemical change induced by light.

Physical Change: A rainbow will appear when water droplets form in air and this can provide a dramatic color appearance. In fact, the color is again not the color of the droplet but the way diffraction splits the light into different colors as seen by the observer.

A physical change that is associated with a true change in actual color (not a change in light scattering) is quite exotic and no good example of such a change has been given in this answer.

Answer 2

A rainbow is a physical change because it involves the dispersion and reflection of light within water droplets in the atmosphere, creating the appearance of a spectrum of colors. The colors are a result of the bending and separation of light as it passes through the water droplets, without any change in the chemical composition of the water or light.

Answer 3

Ordinary yellow sunlight becomes a rainbow when different frequencies of light are bent in slightly different directions.

Answer 4

physical

Answer 5

chemical