Light that shines onto the face of a solar cell or module.

A plot of the change in brightness, expressed in apparent magnitudes, against time of variable stars.

The trapping of light inside a semiconductor material by refracting and reflecting the light at critical angles; trapped light will travel further in the material, greatly increasing the probability of absorption and hence of producing charge carriers.

Defects, such as dangling bonds, induced in an amorphous silicon semiconductor upon initial exposure to light.

The distance traveled by a beam of light in a vacuum in one year, approximately 9.46 trillion (million million) kilometers or 5.99 trillion miles.

An an average speed of 186,291 miles or 299,792 kilometers, per second; which equals approximately 5.88 trillion miles or 9.4607 trillion kilometers, or 63,246 astronomical units.

The light-year is also divided into light-minutes and light-seconds; for example, the moon is 1.3 light-seconds from the earth; the sun is 8.3 light-minutes away from the earth.

Although a light-year is a measurement of distance and not time, it does imply time; such as, the light from a star that is ten light-years from the earth takes ten years to reach the earth; so, an observer on earth is seeing the star as it appeared ten years ago.

Light from the sun that comes into a room through windows or skylights.