5
MCQ (Single Correct Answer)
$\mathrm{O}_2$ molecule consists of two oxygen atoms. In the molecule, nuclear force between the nuclei of the two atoms
A
is not important because nuclear forces are short-ranged
B
is as important as electrostatic force for binding the two atoms
C
cancels the repulsive electrostatic force between the nuclei
D
is not important because oxygen nucleus have equal number of neutrons and protons
6
MCQ (Single Correct Answer)
Two H atoms in the ground state collide inelastically. The maximum amount by which their combined kinetic energy is reduced is
A
10.20 eV
B
20.40 eV
C
13.6 eV
D
27.2 eV
7
MCQ (Single Correct Answer)
A set of atoms in an excited state decays
A
in general to any of the states with lower energy
B
into a lower state only when excited by an external electric field
C
all together simultaneously into a lower state
D
to emit photons only when they collide
8
MCQ (Multiple Correct Answer)
An ionised H -molecule consists of an electron and two protons. The protons are separated by a small distance of the order of angstrom. In the ground state.
A
the electron would not move in circular orbits
B
the energy would be (2) ${ }^4$ times that of a H -atom
C
the electrons, orbit would go around the protons
D
the molecule will soon decay in a proton and a H -atom
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