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
Answer Your brain can't see heat, ultraviolet light, radiowaves,  X-Rays, etc. with your naked eyes, because these different kinds of  light's wavelengths are either too lon â¦ g or too short for your naked  eyes to see. So that is why you can't see infrared.he two ligh energy waves that you can't see are ultra-violet (UV), and infra-red (IR).  Ultra-violet light waves are measured at 380nm and below, infra-red light waves are â¦ 750nm and above.  Normal light that you can see resides between these two regions.