NCERT Class XII Chapter
Atoms
Questions With Solutions

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Question : 17
Total: 18
Obtain the first Bohr’s radius and the ground state energy of a muonic hydrogen atom [i.e., an atom in which a negatively charged muon (µ) of mass about 207 me orbits around a proton].
Solution:  
In Bohr’s model, the radius of nth orbit, r =
n2h2ε0
πZme2

In the given muonic hydrogen atom, a negatively charged muon (µ) of mass 207 me revolve around a proton.
Therefore radius of electron and muon can be written as
rµ
re
=
me
mµ
=
me
207me

rµ =
re
207
=
0.53×1010
207
m = 2.5 × 1012 m
Energy of electron in the orbit, E = -
me4
8ε0n2h2
Ee
Eµ
=
me
mµ
=
me
207me

Eµ = 207 Ee = 207 [- 13.6 eV] = - 2.8 keV
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