Light Wave



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                It is the part of the spectrum that is detected by the human eye. It runs from about to about or a wavelength range of about 700 – 400 nm. Visible light emitted or reflected from objects around us provides us information about the world. Our eyes are sensitive to this range of wavelengths. Different animals are sensitive to different range of wavelengths. The band of visible range falls in between infra red region and ultra violet region. Visible light waves are made up of seven different colors. Each color has a different wavelength (frequency). Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. The pictorial representation of the range of visible light waves is as following:

                The light is transverse in nature; its speed depends on electric and magnetic properties of the medium in which these are travelling. The velocity of electromagnetic waves in free space or vacuum is fixed m/s and thus become important fundamental constant. It has been shown by experiments on electromagnetic waves of different wavelengths that this velocity is the same (independent of wavelength) to within a few meters per second. The constancy of the velocity of waves in vacuum is so strongly supported by experiments and the actual value is so well known now that this is used to define a standard of length. The expression of speed of light in vacuum is as:

                                               (symbols have their usual meaning).

While in the medium speed of light has following relation with speed of light in free space or vacuum):

                                               (symbols have their usual meaning).