Reid Frazier, age 13, of Winchester, Massachusetts, for his question:

What is black light?

Light is a form of electromagnetic energy pulsing along in an assortment of wave lengths. The colors we see are within a rather narrow range of different wave lengths called the visible spectrum. The longest are the reds. But there are wave lengths of light at both ends of the spectrum that are just beyond our range of visi¬bility. A band of shorter waves lies just beyond the shortest violet rays within our range. Their radiation is called ultraviolet, invisible light or black light.

Ultraviolet light makes a more vivid impression on photographic film than does ordinary visible light. Its invisible energy causes certain oils and minerals to become fluorescent. We can see them glowing in the darkness but we cannot see the ultraviolet light that makes them glow. Special lamps are designed to glow with ultra¬ violet energy. Their so called black light can be seen in the surrounding darkness but the ultraviolet rays that cause it are invisible.