Qualm entered English in the 16th century, with meanings like doubt and uneasiness.. Usually a qualm comes from doubt about an action and a feeling that you are doing, or are about to do, something wrong. It isnt a bad feeling about another person's behavior but about your own.
Fluorescent lamps-These have the advantage of higher light efficiency with low heat. This type of lamp is the most widely used for supplemental light. It is available in a variety of colors but cool-white lamps are the most common.
Other sources include: 1  Tanning booths. 2  Mercury vapor lighting (often found in stadiums and school gyms) 3  Some halogen, fluorescent, and incandescent lights. 4  Some types of lasers.