o and B o is equal to the speed of electromagnetic wave and is equal to speed of light c . c In any medium, the ratio of E o and B o is equal to the speed of electromagnetic wave in that medium. Thus v = < c Further, the energy of electromagnetic waves comes from the energy of the oscillating charge. EXAMPLE .
Compute the speed of the electromagnetic wave in a medium if the amplitude of electric and magnetic fields are × N C – and × – T, respectively. Solution The amplitude of the electric field, E o = × N C – The amplitude of the magnetic field, B o = × – T. Therefore, speed of the electromagnetic wave in that medium is v = ms 12th - 12th - - - - - Unit Electromagnetic waves It has less penetrating power. It can be absorbed by atmospheric ozone and is harmful to human body.
It is used to destroy bacteria in sterilizing the surgical instruments, burglar alarm, to detect the invisible writing, finger prints and also in the study of atomic structure. X-rays It is produced when there is sudden stopping of high speed electrons at high- atomic number target, and also by electronic transitions among the innermost orbits of atoms. The frequency range of X-rays is from Hz to Hz. X-rays have more penetrating power than ultraviolet radiation.
X-rays are used extensively in studying structures of inner atomic electron shells and crystal structures. It is used in detecting fractures, diseased organs, formation of bones and stones, dehydrated fruits, in green houses to keep the plants warm, heat therapy for muscular pain or sprain, TV remote as a signal carrier, to look through haze fog or mist and used in night vision or infrared photography. Visible light It is produced by incandescent bodies and also it is radiated by excited atoms in gases.