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Radiation, Ultraviolet
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:
| Table 1: Conventional subdivisions of UV radiation | ||
|---|---|---|
| Name | Wavelength | Comments |
| 1. Near | 400 nm–200 nm | Referred to as ‘Blacklight’ |
| UV-A | 400 nm-320 nm | Strongly absorbed by O3 |
| UV-B | 320 nm-280 nm | Strongly absorbed by O3 |
| UV-C | 290 nm-200 nm | Strongly absorbed by O2 |
| 2. Far | 200 nm-31 nm | Strongly absorbed by O2 |
| 3. Extreme | 31 nm-1 nm | |
In humans, UV radiation is important for ...
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