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
The Invisible Man (1975 TV series) effect of his work is the ability to turn objects invisible, and tries to find medical applications for his invention. He discovers that objects that are made invisible reappear after a few hours, and on living test animals the collars they wear re-appear before the living cells themselves. Obsessed by his invention, Westin decides to become invisible himself, in part to prove that a human can survive the process, and also to test a serum he has developed to reverse the invisibility. He reveals the process to his boss, Walter Carlson (Jackie Cooper), who is initially unimpressed by what he