On a beautiful afternoon you can go outside and feel the sunlight on your face, light that has traveled about 93 million miles over 8 minutes to get to you and make daylight for plants to grow. Later in the afternoon it may rain. Rain clouds may block out the sun but it is still shining. Water will rain down and provide a second vital input for plants. And after the storm, the clouds may part and some sunlight may break through and shine through the rain. When photons hit the rain drops they change from travelling through air to travelling through water, and so they will refract. When sunlight shines through raindrops, the white light is refracted apart into its pieces, and we see Roy G. Biv. Rainbows are formed by the refraction of sun light (white light) through rain drops.