In ascending power of frequencies: radiowaves, microwaves, ultraviolet rays, X-rays and gamma rays. Uses of Electromagnetic Spectrum
(i) γ -rays are highly penetrating, they can penetrate thick iron blocks. Due to high energy, they are used to produce nuclear reactions. γ -rays are produced in nuclear reactions. In medicine, they are used to destroy cancer cells.
(ii) X-rays are used in medical diagnostics to detect fractures in bones, tuberculosis of lungs, presence of stone in gallbladder and kidney. They are used in engineering to check flaws in bridges. In physics X-rays are used to study crystal structure.
(iii) Radiowaves are used for broadcasting programmes to distant places. According to frequency range, they are divided into following groups
(1) Medium frequency band or medium waves 0·3 to 3 MHz
(2) Short waves or short frequency band 3 MHz — 30 MHz
(3) Very high frequency (VHF) band 30 MHz to 300 MHz
(4) Ultrahigh frequency (UHF) band 300 MHz to 3000 MHz
(iv) Microwaves are produced by special vacuum tubes, namely; klystrons, magnetrons and gunn diodes. Their frequency range is 3 GHz to 300 Ghz. They are used in radar systems used in air craft navigation and microwave users in houses.
