Experiments With UV Lights

Written by brian baer
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Experiments With UV Lights
UV light is short for ultraviolet light. (nventilateur_pc image by Rémi Gerard from Fotolia.com)

UV is short for ultraviolet light. Invisible to the naked eye, UV light has a shorter wavelength than visible light, which increases its energy. UV light is also called "black light" and causes certain materials to glow or fluoresce brightly. The energy from black light excites the molecules to reflect back light, often in a colour different from the one expected.

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Ultraviolet Energy Beads

Ultraviolet energy beads are indicators of the presence of UV light. They are normally opaque (no colour) but change to bright colours upon exposure to UV light. Modern sunscreen lotions are designed to block certain harmful UV rays from the sun. An interesting experiment is to buy several different sunscreen lotions with varying sun protection factors (SPF). Place a handful of ultraviolet energy beads in several clear plastic baggies. Apply the sunscreen lotions on the outside of each baggie and label them. Expose the baggies to sunlight for five minutes each and determine if the sunscreen effectively blocks UV light by making a note of the colour (if any) of the beads.

Energy beads change colour when exposed to UV light.
Energy beads change colour when exposed to UV light. (blue beads image by Milissenta from Fotolia.com)

Invisible Ink

Since UV light excites the molecules of certain materials, causing them to emit light back or glow, an experiment can be conducted using petroleum jelly as a type of invisible ink. Using a white piece of paper and a jar of petroleum jelly, write a secret message on the paper. Simply dip a finger into the jelly and write or draw something on the paper. It looks clear and invisible. When the room lights are turned off and the black lights are turned on, the invisible message glows and can be read. A battery-powered black light can be found at most hardware stores.

Experiments With UV Lights
Petroleum jelly makes invisible ink with UV light. (bottle of ink image by Alfonso d'Agostino from Fotolia.com)

Surprise Glowing Objects

With the room lights off, and the black light turned on, many objects will begin to glow. White clothing, neon-coloured paper and highlighter marks all fluoresce under UV light. Outside at night, many minerals, such as calcite and willemite, will glow with bright colours. Certain insects such as scorpions also glow under a black light. This experiment can take many forms and be done in various locations.

Experiments With UV Lights
Black lights can be battery powered. (a flashlight image by timur1970 from Fotolia.com)

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