Pub. date: 2008 | Online Pub. Date: April 25, 2008 | DOI: 10.4135/9781412963893 | Print ISBN: 9781412958783 | Online ISBN: 9781412963893| Publisher:SAGE Publications, Inc.About this encyclopedia
ULTRAVIOLET RADIATION WAS discovered as a result of the observation that silver salts darken on exposure to sunlight. In 1801, the German physicist Johann Wilhelm Ritter first observed that invisible electromagnetic radiation was responsible for this darkening. These rays eventually became known collectively as UV, so named as this radiation is immediately beyond violet in the electromagnetic spectrum. This implies that UV is more energetic than the visible light. Conventionally, UV radiation is broken down into further subdivisions as shown in Table 1 : Name Wavelength Comments 1. Near 400 nm–200 nm Referred to as ‘Blacklight’ UV-A 400 nm-320 nm Strongly absorbed by O 3 UV-B 320 nm-280 ...