Rainbows are produced by:

1. Refraction

   Partly correct. Light entering the raindrop is reflected off of the back surface.

2. Reflection

   Partly correct. As the light passes from air to water, and from water to air, the light is bent or refracted. Different colors are refracted different amounts, separating the colors.

3. Both reflection and refraction

   Correct! When you see a rainbow, the sun will always be behind you. (There are other, similar looking phenomena which you see when facing the sun, but they are not rainbows.) The sunlight enters each raindrop, is refracted (bent). Different colors are refracted different amounts. When the light hits the far side of the raindrop, part of it goes on through, and part of it is reflected back towards the sun (and towards you.) As it passes leaves the drop, the difference in density from water to air refracts (bends) the light even more, separating the colors into bands for the rainbow.

4. Neither reflection no refraction

   No. One or both take part in producing the rainbow.

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