Lights and Lighting

Very basically, two types of lights are required for a veiled chameleon and both are of equal importance.
A flourescent tube that provides UVB radiation and a basking light that provides heat.
UVB is essential to the chameleons ability to absorb and process calcium. This is obviously important in the growth and formation of bones and bone density. Vitamin D3 is the catalyst and can only be created in the body by exposure to the sun.
A UVB bulb attempts to recreate natural sunlight and allow the body to produce D3.
Of course no light is as good as the natural sun, but sunning your chameleon outside is not always possible. When housed in an indoor enclosure, the UVB bulb must be used 10 to 12 hours per day.
The most commonly recommended tube is the Zoomed 5.0, Compact or "screw in" UVB bulbs are not recommended.
The UVB tube has a lifespan. The Zoomed tube should be replaced every 6 months as it's effectiveness diminishes over time.
The basking light is much less specific. It needs to be a white light, and it needs to bring the basking spot to the appropriate temperature (see temperatures and thermoregulation). It should not be housed within the enclosure and it should not heat any part of the enclosure to a temperature that could cause the chameleon to be burned.
Ideally this fixture should be clamped or hung outside the enclosure at a few inches distance, pointed toward one corner where a basking branch has been secured.
A thermometer will need to be utilized io ensure the desired temperatures are achieved. Temperatures can be raised or lowered to the desired level by experimenting with different bulb wattages.
A common household lightbulb is sufficient for this job.
Often the UVB bulb and basking light do not provide enough light for viewing of the animal or for the benefit of the live plants in the enclosure. Additional lighting can be utilized, provided it does not adversely effect the temperatures in the enclosure.