Our view of the sky at night is possible because of the emission and reflection of light. 'Light' is the better-known term for the electromagnetic spectrum, which includes waves in the visible, ultra-violet, infra-red, microwave, radio, X-ray and gamma-ray regions. The scale of the spectrum is so large that no region is distinct, several overlap each other.
A rainbow is an arc of colour in the sky that can be seen when the sun shines through falling rain. The pattern of colours start with red on the outside and changes through orange, yellow, green, blue, indigo, to violet on the inside. Sometimes a second, larger, dimmer rainbow is seen. A rainbow is created when white light is bent while entering a droplet of water, split into separate colours.