What is the origin of the idiom "let there be light" and when to use it?

The idiom "let there be light" is a biblical reference from the book of Genesis in the Bible. In the creation story, it is used to describe God's command for light to exist and illuminate the darkness. Figuratively, "let there be light" is often used to express the act of bringing illumination or clarity to a situation. When used in the context of turning on a light, it can be seen as a playful or poetic way to announce the arrival of light in a room or space, creating a brighter and more visible environment.