NEET Questions Solved

NEET - 2010

The electron in the hydrogen atom jumps from excited state n=3 to its ground state n=1 and the photons thus emitted irradiate a photosensitive material. If the work function of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron in nth state En=13.6n2eV)

(a) 5.1 V                                               (b) 12.1 V

(c) 17.2 V                                              (d) 7 V

For n=1, E1=13.6(1)2=-13.6 eVand for n=3, E3=-13.6(3)2=-1.51 eVSo, required energy  E=E3-E1=-(1.51)-(-13.6)                      =12.09 eV               E=W+eV             eV=E-W                  eV=(12.09-5.1) e                    V=7 volt

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