Q.What are ultraviolet rays? Give two uses.

[!TLDR] Ultraviolet rays are high-energy EM waves just beyond violet light; they are used for sterilising instruments/water and for detecting forged documents or fake gems. [!ANSWER] High-energy EM waves beyond violet light; uses: sterilising …

Ultraviolet (UV) rays, as described in section 13.3.5, are high-energy electromagnetic waves discovered by J. Ritter in 1801, produced by sources such as mercury vapour lamps and the Sun (though most solar UV is absorbed by the ozone layer). Two representative uses from the same section: because UV rays destroy germs and bacteria, they are used for sterilising surgical instruments and for water purification; and because they interact distinctively with certain materials, they are also used to distinguish real gems from fake ones and to detect forgery (other valid uses …

Confusing ultraviolet with infrared uses (e.g. citing heating or thermal-imaging applications, w …