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) as such: "I'd go in and say, 'The song has gone, whatever it is you liked about this song is not there anymore. Sometimes, for example, the song would have disappeared under layers of overdubs." "Ultraviolet (Light My Way)" is written in a 4/4 time signature. The lyrics of "Ultraviolet (Light My Way)" are addressed to a lover, and imply that their relationship is threatened by some sort of personal or spiritual crisis, coupled with a sense of unease over obligations. Indeed, lead vocalist Bono has called the song "a little disturbed". The song opens with 45 seconds of soft