MCQ
The radius of the second Bohr orbit for hydrogen atom is  .......... $\mathop A\limits^o $

(Plank's const. $ h = 6. \times 10^{-34}\, Js\,;$ mass of electron $= 9.1091 \times 10^{-31}\, kg\,;$ charge of electron $e= 1.60210 \times 10^{-19}\, C\,;$ permittivity of vaccum $\in _0 = 8.854185 \times 10^{-12} \,kg^{-1} \,m^{-3} A^2$)

  • A
    $1.65$
  • B
    $4.76$
  • C
    $0.529$
  • $2.12$

Answer

Correct option: D.
$2.12$
d
According to Bohr's theory

$r =0.529 \times \frac{n^{2}}{Z} \mathop A\limits^o $

$ = 0.529 \times \frac{{{2^2}}}{1} = 2.116{\mkern 1mu} \,\mathop A\limits^o $

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