Question

Identify the electromagnetic radiation and write its wavelength range, which is used to kill germs in water purified. Name the two sources of these radiations.

Answer 1

Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, gamma rays, and cosmic rays provide the whole range (electromagnetic spectrum) in increasing frequency and decreasing wavelength order. The type of radiation and their frequency and wavelength ranges are as follows:

Types of Radiation	Frequency Range (Hz)	Wavelength Range
Gamma-rays	1020 - 1024	< 10-12 m
X-rays	1017 - 1020	1 nm - 1 pm
Ultraviolet	1015 - 1017	400 nm - 1 nm
Visible	4 × 1014 - 7.5 × 1014	750 nm - 400 nm
Near-infrared	1 × 1014 - 4 × 1014	2.5 µm - 750 nm
Infrared	1013 - 1014	25 µm - 2.5 µm
Microwaves	3 × 1011 - 1013	1 mm - 25 µm
Radio waves	< 3 × 1011	> 1 mm

In water purifiers, ultraviolet light is utilised to kill bacteria. The sun is the most powerful source of UV radiation.

UV lamps, arc welding, and mercury vapour lamps are examples of man-made ultraviolet sources. Carbon, Xenon, and other arcs are some of the devices that release UV radiation.