Phy 133 – Assignment 7:
A.
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f = (2.40 x 1018)(.75) = 1.80 x 1018 Hz
B. 1. (a) No. The energy levels in hydrogen are –(13.6 eV)/n2 . That makes
the first and second levels -13.6 eV and -3.4 eV, with the higher levels
getting closer to zero after that. So, the electron would be starting with –
13.6 eV, and there is no level at –3.6 eV for it to end up in.
(b) Yes. This would get the electron up to +.4 eV. An energy of zero or
more knocks the electron right out of the atom. The energy of a free
electron is not quantized, so +.4 eV works just fine.
2.
C. 1. In a neutral atom, the electron being excited is not only attracted to the
nucleus but also repelled by the other electron. Due to this “shielding” by
the other electron, it feels an effective nuclear charge of about (1)e.
In He+, there is no other electron. The nuclear charge of (2)e pulls on the
electron twice as hard as (1)e and therefore twice the energy is needed to
excite it.
2.
D. 1. Classical mechanics does not impose energy levels on the atom. With
no restrictions on how the electron moves, it could radiate at any frequency.
2.
E.
F.