Modern Physics CDS Questions

CDS Physics

Modern Physics MCQ Questions


13.
Niels Bohr's model of the atom, proposed in 1913, introduced the key concept that electrons orbit the nucleus:
A.
Only in a single, fixed orbit, identical for every type of atom
B.
In specific, fixed (quantised) energy levels or orbits, without continuously radiating energy
C.
While constantly radiating away all of their energy until they spiral into the nucleus
D.
In a completely random and unpredictable fashion, with no defined orbits whatsoever
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ANSWER :
B. In specific, fixed (quantised) energy levels or orbits, without continuously radiating energy
14.
According to Bohr's model, an atom emits a photon of light when an electron:
A.
Transitions from a lower energy orbit to a higher energy orbit
B.
Remains permanently fixed within a single, unchanging orbit
C.
Is completely removed from the atom entirely (ionisation)
D.
Transitions (jumps) from a higher energy orbit to a lower energy orbit
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ANSWER :
D. Transitions (jumps) from a higher energy orbit to a lower energy orbit
15.
The three fundamental subatomic particles that constitute the basic structure of an atom are:
A.
Protons, photons, and neutrinos
B.
Ions, ligands, and isotopes
C.
Quarks, gluons, and leptons exclusively
D.
Protons, neutrons, and electrons
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ANSWER :
D. Protons, neutrons, and electrons
16.
The atomic number of an element is defined as the number of:
A.
Neutrons present in the nucleus
B.
Electrons present in the outermost shell only
C.
Protons present in the nucleus of an atom of that element
D.
Total nucleons (protons plus neutrons) in the nucleus
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ANSWER :
C. Protons present in the nucleus of an atom of that element
17.
The mass number of an atom is defined as the sum of:
A.
The number of neutrons and the number of electrons
B.
The atomic number and the atomic radius
C.
The number of protons and the number of electrons
D.
The number of protons and the number of neutrons in its nucleus
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ANSWER :
D. The number of protons and the number of neutrons in its nucleus
18.
Isotopes of a given element are atoms that have:
A.
Entirely different chemical properties from one another, despite sharing the same atomic number
B.
Different atomic numbers but identical mass numbers
C.
The same number of protons (and hence the same atomic number) but different numbers of neutrons (and hence different mass numbers)
D.
The same number of neutrons but different numbers of protons
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ANSWER :
C. The same number of protons (and hence the same atomic number) but different numbers of neutrons (and hence different mass numbers)