adam85491 wrote:A simple incandescent house bulb will supply your turtle with sufficient UVA rays while meeting the requirement for heat.
I hope this is helpful:
Incandescent light bulbs do not emit UVA, or we would all have skin cancer from sitting indoors at night with our incandescent light bulbs turned on.
10% of light given off from an Incandescent light bulb is from the Visible portion of the electromagnetic spectrum. Visible light ranges from red (lower frequency) across the rainbow of colors to violet (higher freqency). It allows us to see colors. Visible light has lower frequencies and longer wavelengths than UVA/B.
The remaining 90% of light emitted from an Incandescent bulb is from the Infrared portion of the em spectrum (below red, below the Visible light range with even lower frequencies/longer wavelenghts), as heat. Infrared light is useful as a heat source. This is why Incand. bulbs get so hot.
Ultraviolet light is not visible (black/dark) to us (ultraviolet means above/beyond violet on the em spectrum; in other words, above the Visible range) and has dangerously high frequencies, which can cause skin cancer. UV gives off a small amount of heat.
Light emitted from UVA and UVB lamps are not safe to look at directly, just as you should never look directly at the sun (it can blind you), so be careful when installing and using your UVA and/or UVB light sources.
Glass and plexiglass both block UVA/B light. (The glass of the UVA/B bulb itself is designed to not block that UV light, of course.) Water blocks about 50% of the light. You can protect your eyes if you position glass or plexiglass between you/your eyes and the UV source.
You might check out this url to read about light:
http://www.answers.com/topic/light
Very well done. About a quarter of the way down, you will find information on incandescent light.