^γ – rays (a) Produced in nuclear reactions and are also emitted by radioactive nuclei (such as Co 60 & Cs 137). (b) Properties: Effect on photographic plate, fluorescence, ionization, diffraction, high penetrating power & can cause serious damage if absorbed by living tissues. (c) Used in radio therapy to treat certain cancers and tumors to […]
^Ultraviolet light (a) Produced by special lamps like mercury and iron are lamps and by very hot bodies like sun. (b) Properties: Effect on photographic plate, fluorescence, ionization, highly energetic, tanning of the human skin. (c) Used To destroy bacteria and for sterilizing the surgical instruments In the detection of forged documents finger prints In […]
^Visible light Produced by hot bodies like sun, electric bulbs and tubes etc. as a result of electronic transitions. Our eyes are sensitive to visible light which helps us to collect the information about our surrounding. Properties: Reflection, refraction, interference, diffraction, polarization, photoelectric effect, photographic action, sensation of sight.
^Infra red waves (a) Also called heat waves & are produced by hot bodies and molecules. (b) Properties: Heating effect, reflection, refraction, diffraction & propagation through fog. (c) Used In taking photographs during the conditions of fog, smoke etc. as these waves are scattered less than visible rays and hence can travel longer distances through […]
^Micro waves (a) Produced by special vacuum tubes like klystrons & magnetrons. Due to their shorter wavelengths the microwaves don’t spread or bend around the corners of any obstacle coming in their way, hence can be transmitted as beam signals in a particular direction. (b) Properties: Reflection, refraction, diffraction and polarization. (c) Used in Radar […]
^Radio waves (a) Produced by the charges accelerating through LC oscillators. (b) Properties: Reflection, diffraction (c) Used for wireless communication purposes, like transmission of radio and TV signals and cellular phones.
^Radiation pressure The force exerted by electromagnetic wave on unit area of the surface is called radiation pressure (P). It is defined as If an EM wave of energy U incident normally on a surface of area A then the radiation pressure exerted by the EM wave on the surface is
^Linear momentum of the EM wave EM waves carry energy and momentum. If a portion of EM wave of energy U propagates with speed c, then linear momentum of the EM wave is
^Poynting vector Poynting vector gives intensity of EM – wave & is defined as: SI unit : W/m2
^Intensity of EM waves Intensity of EM wave is defined as the average energy crossing per second per unit area perpendicular to the direction of propagation of electromagnetic wave. i.e.
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