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 My Way) Ultraviolet (Light My Way) "Ultraviolet (Light My Way)" is a song by Irish rock band U2 and the tenth track from their 1991 album "Achtung Baby". Ostensibly about love and dependency, the song also lends itself to religious interpretations, with listeners finding allusions to the Book of Job and writers finding spiritual meaning in its invocation of the light spectrum. The song's composition and recording incorporate both serious and throwaway elements, in keeping with the rest of "Achtung Baby". While not released as a single, the song has appeared in two films and a U2 business venture was named after