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Question
Which wavelengths will be emitted by a sample of atomic hydrogen gas (in ground state) if electrons of energy 12.2 eV collide with the atoms of the gas?
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Solution
As the electron collides, it transfers all its energy to the hydrogen atom.
The excitation energy to raise the electron from the ground state to the nth state is given by
`E = (13.6 eV)xx(1/1^2 - 1/n^2)`
Substituting n = 2, we get
E = 10.2 eV
Substituting n = 3, we get
E' = 12.08 eV
Thus, the atom will be raised to the second excited energy level.
So, when it comes to the ground state, there is transitions from n = 3 to n = 1.
Therefore, the wavelengths emitted will lie in the Lyman series (infrared region).
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