According to Business Wire, in 2003: Ten percent of Americans spend on average $300 per year to tan indoors. This equates to a total US market for tanning of over $9 billion per year, and does not include the $3 billion tanning products market. Enhancements in technology and consumer acceptance are fueling the industry's growth. A suntan is the result of injury to the epidermis, the top layer of your skin.
the most striking example of fluorescence occurs when the absorbed radiation is in the ultraviolet region of the spectrum and thus invisible to the human eye while the emitted light is in the visible region which gives the fluorescent substance a distinct color that can only be seen when exposed to uv light
This means that a yellow object will appear red under red light, and green under green light. Yellow does not contain blue, so it will appear black under blue light. White objects reflect all light, so will appear to be the colour of the light on them. Black objects, conversely, absorb all the light, and do not reflect any, so always appear black. Most white light also contains infra-red, which we cannot see. Infra-red is heat energy.