Ultraviolet Light
Ultraviolet light is a type of light from the sun that human eyes cannot see.
Think of it this way
A radio sits on a kitchen counter next to a lamp. The lamp sends out visible light you can see across the room. The radio sends out invisible radio waves that fill the same space. Ultraviolet light works like that radio signal, it travels from the sun but your eyes cannot detect it.
Explaining ultraviolet light by grade level
Sunlight has colors you can see, like red and blue. It also has light you cannot see at all. That hidden light is called UV light. UV light can hurt tiny living things like yeast and slow them down.