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Hydrogen Emission Spectrum On heating small sample of hydrogen gas, its molecule break down into atoms. The electrons in different hydrogen atoms absorb different amount of energy therefore     jump to different higher energy state (Excited state). The time period for excited state is only 10 -6 to 10 -8 second .So electrons come back to their ground state in one or more jumps by emitting radiation (energy) of different wavelengths. Radiations of different wavelength are obtained as lines. .[Collection of these lines (obtain when electron jump to same energy level)   is called series.   All series   are named after the name of their discoverer. These series are collectively called spectrum.] Fig. Generation of spectral lines in hydrogen spectrum
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Photoelectric effect   Figure : Equipment for studying the photoelectric effect .light strike a clean metal surface inside a vacuum chamber. Electrons are ejected from the metal and are counted by a detector that measure their kinetic energy H.Hertz in 1887 performed an experiment in which-   electrons were ejected when metal like K, Rb and Cs were exposed to a beam of light .This phenomena is called Photoelectric effect. Following results are obtained in this experiment. (i) The electrons are ejected from the metal as soon as light strike on the metal surface . (ii) The number of electron ejected is proportional to the intensity of light. (iii) For each metal, there is characteristic minimum frequency     (also known as threshold frequency ) below which photoelectric effect do not observe and electrons are eject with certain kinetic energy. All the above result could not explain by classical wave theory of light. According to wh...
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CHAPTER- STRUCTURE OF ATOM Relation between intensity ad wavelength Black Body Radiation :    This phenomenon is explained by Max Plank in 1900. When solid is heated it emit radiation over wide range of wavelength .For example when a iron rod is heated it become dull red and then more and more red ,further with increase in temperature it become orange ,yellow ,white and blue at last. The red colour is of higher wavelength and lower frequency and blue colour is of lower wavelength and higher frequency, this means with increase in temperature, wavelength decrease and increase in frequency. An ideal body which emits and absorbs radiation of all wavelengths is called a black body and the radiation emitted by such a body is called black body radiation . Intensity verses wavelength curve depend upon temperature .At a given temperature intensity of radiation emitted increase with decrease of wavelength, it reaches maximum value and then decrease with decrease of wav...
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