21.   -- A security thread that will glow red when exposed to ultraviolet light.

22.   A beam of ultraviolet light passes through the molds, which are made of glass and quartz, and essentially cooks the liquid into a gel in seconds.

23.   A hospital that sees many TB patients will need specially designed ventilation systems and ultraviolet light to clean the air, as well as special masks for the staff.

24.   A thinner ozone layer allows more ultraviolet light to reach the Earth, he points out, and ultraviolet light has damaged frog embryos in lab experiments.

25.   A. Sunscreens protect your skin either by absorbing ultraviolet light, or by reflecting or scattering light away from your skin, says Taylor.

26.   A wall of windows exposes the collection to ultraviolet light, despite the addition of blinds and UV filters.

27.   A. There are several ways to simulate a tan without actually exposing your skin to dangerous ultraviolet light.

28.   Alain Boucar flips open a passport and holds it under an ultraviolet light.

29.   But there is no evidence that ultraviolet light can cause missing legs, Ankley concedes, especially at the only slightly elevated levels found in nature.

30.   But what is it about ultraviolet light that melanin protects against?