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Published on: 23/05/2021
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Download CBSE Class 12th Standard CBSE Physics question papers, sample papers, important questions, and previous year solved papers in PDF format. Get free study materials, NCERT solutions, and exam preparation resources for Class 12th Standard CBSE Physics
Questions + Answers key
Take MCQ Physics Test1.
The Balmer series for the H-atom can be observed
if we measure the frequencies of light emitted when an excited atom falls to the ground state
if we measure the frequencies of light emitted due to transitions between excited states and the first excited state
in any transition in a H-atom
as a sequence of frequencies with the higher frequencies getting closely packed.
2.
The Bohr model for the spectre of a H-atom
will not be applicable to hydrogen in the molecular form
will not be applicable as it is for a He-atom
is valid only at room temperature
predicts continuous as well as discrete spectral lines
3.
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,
because of energy conservation
without simultaneously releasing energy in the form of radiation
because of momentum conservation
because of angular momentum conservation.
4.
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
the electron would not move in circular orbits
the energy would be (2)4 times that of a H-atom
the electrons, orbit would go around the protons
the molecule will soon decay in a proton and a H-atom.
5.
For the ground state, the electron in the H-atom has an angular momentum =h, according to the simple Bohr model. Angular momentum is a vector and hence there will be infinitely many orbits with the vector pointing in all possible directions. In actuality, this is not true,
because only one of these would have a minimum energy
because only one of these would have a minimum energy
angular momentum must be in the direction of spin of electron
because electrons go arround only in horizontal obits.
1.
(b)
if we measure the frequencies of light emitted due to transitions between excited states and the first excited state
2.
(b)
will not be applicable as it is for a He-atom
3.
(b)
without simultaneously releasing energy in the form of radiation
4.
(c)
the electrons, orbit would go around the protons
5.
(a)
because only one of these would have a minimum energy
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