Black lights look just like normal fluorescent lamps or incandescent light bulbs , but they do something completely different. Switch one on, and white clothes, teeth and various other things glow in the dark , while the bulb itself only emits faint purple light.

Our eyes can see visible light in a spectrum ranging from red through orange, yellow, green, blue and violet. Above violet is ultraviolet light, which we cannot see.

While products that "Glow in the Dark" are non toxic and relatively harmless, they work better with exposure to light sources with UV rays in them. A good example is Sunlight. Sunlight arrives on earth in three forms: infrared (heat), visible light and ultraviolet. Ultraviolet light is classified into three categories:

• Longwave - UVA (315 to 400 nm), also known as black light, which causes tanning
• Mediumwave - UVB (280 to 315 nm), which causes damage in the form of sunburn
• Shortwave - UVC (100 to 280 nm), which is filtered out by the atmosphere and never reaches us.

As mentioned above, Glow in the Dark products get charged faster with a UV light source, 'A', ' B' or 'C'.

Ultra Violet Light Sensitive products work only under UV lights.

UV light can also be used for other applications like:

• detecting counterfeit money
• detecting forgeries
• clubs use them to identify patrons by hand stamping
• can also be used to test leaks or emissions.

It is a known fact that UV 'A' is the least harmful uv light source - the kind produced by blacklights. While UVA is safe for normal usage, it is not advisable to stare at the UV lamps for long periods.