![]() Rydberg in 1890 gave a very simple theoretical equation for the calculation of wavelength of these lines. When hydrogen gas at low pressure is taken in the discharge tube and the light emitted on passing electric discharge is examined with a spectroscope ,the spectrum obtained is called the emission spectrum of hydrogen.It is found to consist of a large number of lines which are grouped into different series ,named after the discoverer. The spectrum thus obtained is called absorption spectrum. The wavelength absorbed were same as were emitted in the emission spectra. The dark lines are at the same place where coloured lines are obtained in the emission spectra for the same substance. These dark lines are supposed to result from the fact that when the white light is passed through the chemical substance, the radiations of certain wavelengths are absorbed, depending upon the nature of the element. ![]() White light from any source is passed through the solution or vapours of a chemical substance and then analysed by the spectroscope, it is observed that some dark lines are obtained. This spectrum is called line emission spectrum on line spectrum.Įach line in the spectrum corresponds to a particular wavelength. If this light is resolved in a spectroscope, some isolated coloured lines are obtained on the photographic plates separated from each other by dark spaces. Sodium emits yellow light while potassium gives out violet light. The colour of light emitted depends upon the nature of substance. When some volatile salt is placed in the bunsen flame or an electric discharge is passed through a gas at low pressure, light is emitted. On passing through the prism, red colour with the longest wavelength is deviated least while violet colour with shortest wavelength is deviated the most. ![]() Hence the spectrum is called continuous spectrum. These colours are so continuous that each of them merges into the next. When white light from any source is analysed by passing through a prism, it is observed that it splits up into 7 different wide bands of colour. ![]()
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