Rainbows are caused by the refraction of sunlight through water droplets in the atmosphere. As sunlight passes through a water droplet, it is refracted, or bent. The different colors of light are refracted at different angles, causing them to separate into a rainbow.

The corona is a halo that appears around the sun or moon. It is caused by the diffraction of sunlight or moonlight through ice crystals in the atmosphere.

Mirages are caused by the refraction of light through air of different temperatures. When light passes from one layer of air to another with a different temperature, it is refracted, or bent. This can cause objects to appear to be higher or lower than they actually are.

The sky appears blue due to Rayleigh scattering. Rayleigh scattering is the scattering of light by particles that are much smaller than the wavelength of light. In the case of the sky, the particles that scatter light are molecules of nitrogen and oxygen.

The sky appears red at sunrise and sunset due to Mie scattering. Mie scattering is the scattering of light by particles that are about the same size as the wavelength of light. In the case of the sky at sunrise and sunset, the particles that scatter light are dust particles and water droplets.

The green flash is caused by Rayleigh scattering. Rayleigh scattering is the scattering of light by particles that are much smaller than the wavelength of light. In the case of the green flash, the particles that scatter light are molecules of nitrogen and oxygen.

The corona is a halo that appears around the sun or moon. It is caused by the diffraction of sunlight or moonlight through ice crystals in the atmosphere.

A sundog is a bright spot that appears to the left or right of the sun. It is caused by the refraction of sunlight through ice crystals in the atmosphere.

A parhelion is a bright spot that appears directly above or below the sun. It is caused by the refraction of sunlight through ice crystals in the atmosphere.

A circumzenithal arc is a colorful arc that appears around the zenith. It is caused by the refraction of sunlight through ice crystals in the atmosphere.

A glory is a colorful ring that appears around the shadow of an observer's head. It is caused by the diffraction of sunlight through water droplets in the atmosphere.

Crepuscular rays are rays of sunlight that appear to radiate from the sun at sunrise and sunset. They are caused by the scattering of sunlight through dust particles and water droplets in the atmosphere.

Noctilucent clouds are thin, wispy clouds that appear at high altitudes in the mesosphere. They are caused by the condensation of water vapor on ice crystals in the mesosphere.

Polar stratospheric clouds are thin, wispy clouds that appear in the stratosphere at high latitudes. They are caused by the condensation of water vapor on ice crystals in the stratosphere.