NEET Sample Paper NEET Sample Test Paper-65

  • question_answer
    The frequency of radiations emitted when electron falls from \[\operatorname{n}= 4 \,to\,\,n =1\] in H-atom would be (Given \[{{G}_{1}}\,for\,\,H=2.18\,\,\times \,\,1{{0}^{-\,18}}\,J\,\,ato{{m}^{-\,1}}\] and \[h=6.625\times {{10}^{-34}}\,Js.\]

    A) \[1.54\times 1015\,{{s}^{-}}^{1}\]      

    B) \[1.03\times 1015\,{{s}^{-}}^{1}\]

    C) \[3.08\times 1015\,{{s}^{-}}^{1}\]      

    D) \[2.0\times 1015\,{{s}^{-}}^{1}\]

    Correct Answer: C

    Solution :

    Ionisation energy of \[H=2.18\times {{10}^{-}}^{18}J\text{ }ato{{m}^{-}}^{1}\] \[\therefore \,\,{{E}_{1}}\] (energy of 1st orbit of H-atom) \[=-2.18\,\,\times \,\,{{10}^{-}}^{18}J\text{ }ato{{m}^{-1}}\] \[\therefore \,\,\,{{E}_{n}}=\frac{-2.18\times {{10}^{-18}}}{{{n}^{2}}}\,\,J\,\,at{{m}^{-\,1}}\] \[Z=\text{1 }for\text{ }H-atom\] \[\Delta E\,\,=\,{{E}_{n}}-{{E}_{1}}=\frac{-2.18\times {{10}^{-}}^{18}}{{{4}^{2}}}\,\,-\,\,\frac{-2.18\times {{10}^{-}}^{18}}{{{l}^{2}}}\] \[\Delta E\,\,=\,\,\,-2.18\times {{10}^{-}}^{18}\,\times \,\frac{-15}{16}\] \[= \,+2.0437 \times  1{{0}^{-}}^{18}J atom{{\,}^{-}}^{1}\] \[\nu =\frac{\Delta E}{h}\,\,=\,\,\frac{2.04\times {{10}^{-18}}}{6.626\times {{10}^{-34}}}\,\,=\,\,3.084\times {{10}^{15}}\,{{s}^{-\,1}}\,atom{{\,}^{-\,1}}\]


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