In the first excited state of hydrogen atom, the energy of its electron is -3.4 eV . The radial distance of the electron from the hydrogen nucleus in this case is approximately: (Take 1 eV =1.6 10 -19 J , e=1.6 10 -19 C and 1 4 0 =9 10 9 N m 2/C 2 )

1. A. 2.1 10 -8 m
2. B. 2.1 10 -10 m
3. C. 2.1 10 -11 m
4. D. 2.1 10 -9 m

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