Photoacoustic spectroscopy Photoacoustic spectroscopy Photoacoustic spectroscopy is the measurement of the effect of absorbed electromagnetic energy (particularly of light) on matter by means of acoustic detection. The discovery of the photoacoustic effect dates to 1880 when Alexander Graham Bell showed that thin discs emitted sound when exposed to a beam of sunlight that was rapidly interrupted with a rotating slotted disk. The absorbed energy from the light causes local heating, generating a thermal expansion which creates a pressure wave or sound. Later Bell showed that materials exposed to the non-visible portions of the solar spectrum (i.e., the infrared and the ultraviolet) can
Ultraviolet light therapy practices for the treatment of cosmetic skin conditions (such as psoriasis, acne, eczema and vitiligo) and in indoor tanning salons for cosmetic tanning. At least 88 percent of dermatologists recommend the usage of tanning equipment or salon tanning for clients to inexpensively self-treat skin conditions as a convenient alternative for clients in rural locations, as well as naturally occurring exposures including ultraviolet light from the sun. Typical treatment regimens involve short exposure to UVB rays 3 to 5 times a week at a hospital or clinic, and repeated sessions may be required before results are noticeable. Almost all of the