9
MCQ (Multiple Correct Answer)
Consider aiming a beam of free electrons towards free protons. When they scatter, an electron and a proton cannot combine to produce a H -atom.
A
Because of energy conservation
B
Without simultaneously releasing energy in the form of radiation
C
Because of momentum conservation
D
Because of angular momentum conservation
10
MCQ (Multiple Correct Answer)
The Bohr model for the spectra of a H -atom
A
will not be applicable to hydrogen in the molecular from
B
will not be applicable as it is for a He -atom
C
is valid only at room temperature
D
predicts continuous as well as discrete spectral lines
11
MCQ (Multiple Correct Answer)
The Balmer series for the H -atom can be observed
A
if we measure the frequencies of light emitted when an excited atom falls to the ground state
B
if we measure the frequencies of light emitted due to transitions between excited states and the first excited state
C
in any transition in a H -atom
D
as a sequence of frequencies with the higher frequencies getting closely packed
12
MCQ (Multiple Correct Answer)
Let $E_n=\frac{-1 m e^4}{8 \varepsilon_0^2 n^2 h^2}$ be the energy of the $n$th level of H -atom. If all the H -atoms are in the ground state and radiation of frequency $\frac{\left(E_2-E_1\right)}{h}$ falls on it,
A
it will not be absorbed at all
B
some of atoms will move to the first excited state
C
all atoms will be excited to the $n=2$ state
D
no atoms will make a transition to the $n=3$ state
13
MCQ (Multiple Correct Answer)
The simple Bohr model is not applicable to $\mathrm{He}^4$ atom because
A
$\mathrm{He}^4$ is an inert gas
B
$\mathrm{He}^4$ has neutrons in the nucleus
C
$\mathrm{He}^4$ has one more electron
D
electrons are not subject to central forces