|
tanning. Extended exposure can lead to
eye damage and skin cancer in light-skinned
people. Skin cancer is rare in dark-skinned
people. Although transparent to lower-energy ultraviolet light, glass blocks higher energy ultraviolet light. Lotions that are advertised as Sun blockers also block higher energy ultraviolet light. When the glass is inserted between the lamp and the fluorescing material in this demonstration, the fluorescence diminishes or stops. Some materials fluoresce with lower energy ultraviolet waves as well as the higher energy waves, and any continued fluorescence is the result of the lower energy waves. Ultraviolet light tells astronomers several things. For example, the local neighborhood of our SunQwithin 50 light yearsQcontains many thousands of low-mass stars that glow in the ultraviolet. When low-mass stars use up all their fuel, they begin to cool. Over billions of years, the internal heat left over from stellar fusion reactions radiates into space. This leftover heat contains a great deal of energy. These stars, called white dwarfs, radiate mostly ultraviolet light. Until astronomers could make observations with ultraviolet telescopes in space, they had very little information about this phase of a star's evolution. Caution: Do not look into the light emitted by the broad spectrum ultraviolet lamp. |
Avoid directing the light to reflective
surfaces. Everyone should wear eye
protection such as laboratory safety glasses
or ordinary eye glasses. Where to Obtain Ultraviolet Lights and Minerals: Many science-supply catalogs sell ultraviolet lights and fluorescent minerals. If you purchase a light, be sure to obtain a broad spectrum light because it will emit both long and short wave ultraviolet light. Order minerals, such as calcite, fluorite, and franklinite, that fluoresce at short wavelengths, long wavelengths, and both long and short wavelengths. If you do not wish to purchase a lamp and minerals, check with other schools to see if they have equipment you can borrow. Also check with local rock and mineral clubs. Many collectors have lights and fluorescent minerals and may be willing to come to your school to give a demonstration. If ultraviolet minerals are not available, experiment with ultraviolet-sensitive paints or paper. For Further Research:
|