Q50 / 201 · NTA Abhyas (NEET) 2020 · Physics · Atomic Physics

The total energy of an electron in the first excited state of hydrogen is about -3.4eV. Its kinetic energy in this state is

  • A
    - 3.4 eV
  • B
    - 6.8 eV
  • C
    6.8 eV
  • Correct answer
    D
    3.4 eV

Solution

The kinetic energy of an electron

    K =Ze28πε0r

The potential energy of an electron

    U =-14πε0Ze2r

∴ Total energy

E = K +U = Ze28πε0r- Ze24πε0r

Or    E=-Ze28πε0r

Or    E=-K

Or     K=-E= -(-3.4)

Or            =3.4 eV

Hence, the correct answer is option: 'D'.

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