To view a rainbow, your back must be to the sun as you look at an approximately 40 degree angle above the ground into a region of the atmosphere with suspended droplets of water or even a light mist.

In a process known as dispersion, each color of light is bent at a slightly different angle due to its different wavelengths. In the case of a rainbow, the sunlight is refracted as it enters the water droplet, which causes the sunlight to disperse, or spread out, into its component colors.

When sunlight enters and exits water droplets at specific angles, it emerges most intensely at about 42 degrees relative to the direction opposite the Sun.

A secondary rainbow appears if the sunlight is reflected twice inside the water droplets. Secondary rainbows are fainter, and the order of the color is reversed, with red on the bottom.

You see a rainbow when sunlight enters raindrops at just the right angles. Since each color bends differently, the light reaching your eyes forms a circle of colors.

Rainbows can be observed whenever there are water drops in the air and sunlight shining from behind the observer at a low altitude angle. Because of this, rainbows are usually seen in the western sky during the morning and in the eastern sky during the early evening.

Red light exits at an angle of 42 degrees, while violet is slightly smaller at 40 degrees. The different angles from multiple droplets form a complete circle of color in the sky — our beloved rainbow.

To view a rainbow, your back must be to the sun as you look at an approximately 40 degree angle above the ground into a region of the atmosphere with suspended droplets of water or even a light mist.

This 42-degree angle is consistent for all raindrops contributing to a visible rainbow for a given observer. Red light exits the raindrop at roughly 42 degrees, while violet light emerges at about 40 degrees, with other colors in between.

The combined effect of countless droplets, each sending a different color at the required angle, produces the bright multicolored arc we call a rainbow. Because the angles are fixed, you see a rainbow only when you stand between the Sun and falling water droplets with your back to the Sun.