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Equipment

Ultra Violet Lamp
AKA: UV Source

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Fig 1: Security type UV blacklight
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Summary

A 'blacklight' bulb used to make items fluoresce using UV radiation.

Operation

Light consists of electromagnetic waves of varying frequencies. Visible light wavelength is measured in billionths of a meter (nanometers) Red light has an approximate wavelength of 700nm, green around 500nm. 400nm is a violet-blue colour and anything with a shorter wavelength than that is usually invisible, however you can ‘see’ this invisible light indirectly by fluorescence.

UV lamps can be purchased though usual lab suppliers or though electrical shops, Maplin for example. It is important that the type of lamp you purchase is safe to use in the classroom. ‘Blacklight’ lamps are UV but are safe as they contain a special coating that ensures that no harmful UV wavelengths are emitted. These type are often sold as ‘disco’ lamps as they are similar to those used in nightclubs to make clothes glow. Safe types also include security UV lamps used in conjunction with a pen to mark items. UV discharge tubes which are sometimes used in physics lessons should not be viewed with the naked eye and so should not be used in this way.

Blacklight UV makes phosphors glow brightly. Phosphors occur naturally in your teeth and fingernails as well as in scales of some tropical fish and some moths. There are lots of phosphors in man made materials such as TV screens, washing powder and banknotes.

Turn the lights off in your store room, power up the UV blacklight and see what items fluoresce. These items can then be included in the accompanying kit. Banknotes have a striking symbol which glows very brightly, phosphor dots on sent mail also can be seen well. A UV security marker is a must. Fluorescent pens also work well as do UV sensitive paints.

Safety

 CautionThe contents of this page are for information only. Please refer to CLEAPSS or ASE safety advice and/or publications before undertaking any preparation, practical experiment or using any equipment featured on this site or any other.