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NCERT Solutions for class 12 Physics | Chapter 12 - Atoms

Questions
1 The binding energy of a deuteron is about:
A 2.22 MeV
B 2.22 J
C 2.22 eV
D None of these

Answer:2.22 MeV
2 Artificial radioactivity was discovered by:
A Joliot
B Becquerel
C Pauli
D None of these

Answer:Joliot
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3 The principle that a quantum orbital cannot be occupied by more than two electrons was given by:
A Pauli
B Millikan
C Hund
D None of these

Answer:Pauli
4 Isotones have the same:
A A
B Z
C N
D All the above

Answer:N
5 Fg and Fe represents the gravitational and electrostatic force respectively between two electrons situated at some distance the ratio  Class 12 Physics Chapter 12 Atoms is if the order of:
A 9.8
B 109
C 1042
D 10-42

Answer:10-42
6 Isobars have the same:
A A
B Z
C N
D All the above

Answer:A
7 Who explained the splitting of special lines in magnetic field?
A Zeeman
B Bohr
C Summerfield
D Einstein

Answer:Zeeman
8 An atom stays in an excited state for about:
A 10 micro seconds
B 10 milli seconds
C 10 nano seconds
D 10 seconds

Answer:10 nano seconds
9 In terms of Bohr radius r0, the radius of the second Bohr orbit of a hydrogen atom is given by
A 4 r0
B 8 r0
C √2 r0
D 2 r0

Answer:4 r0
10 When an atomic gas or vapour is excited at low pressure, by passing an electric current through it then
A emission spectrum is observed
B absorption spectrucm is observed
C band spectrum is observed
D both (b) and (c)

Answer:emission spectrum is observed
11 When hydrogen atom is in its first excited level, it’s radius is
A four times, it ground state radius
B twice times, it ground state radius
C same times, it ground state radius
D half times, it ground state radius.

Answer:four times, it ground state radius
12 Which of the following in a hydrogen atom is independent of the principal quantum number n? (The symbols have their usual meanings).
A νn
B Er
C En
D νr

Answer:Er
13 Which of the following parameters is the same for all hydrogen-like atoms and ions in their ground states?
A Radius of the orbit
B Speed of the electron
C Energy of the atom
D Orbital angular momentum of the electron

Answer:Orbital angular momentum of the electron
14 The electrons of Rutherford’s model would be expected to lose energy because, they
A move randomly
B jump on nucleus
C radiate electromagnetic waves
D escape from the atom

Answer:radiate electromagnetic waves
15 According to classical theory, Rutherford’s atomic model is
A stable
B unstable
C meta stable
D both (a) and (b)

Answer:both (a) and (b)
16 As one considers orbits with higher values of n in a hydrogen atom, the electric potential energy of the atom
A decreases
B increases
C remains the same
D does not increase

Answer:increases
17 Rutherford’s atomic model was unstable because
A nuclei will break down
B electrons do not remain in orbit
C orbiting electrons radiate energy
D electrons are repelled by the nucleus

Answer:electrons do not remain in orbit
18 Electrons in the atom are held to the nucleus by
A coulomb’s force
B nuclear force
C vander waal’s force
D gravitational force

Answer:coulomb’s force
19 The angular speed of the electron in the nth orbit of Bohr hydrogen atom is
A directly proportional to n
B inversely proportional to n
C inversely proportional to n2
D inversely proportional to n3

Answer:inversely proportional to n3
20 The significant result deduced from the Rutherford’s scattering experiment is that
A whole of the positive charge is concentrated at the centre of atom
B there are neutrons inside the nucleus
C α-particles are helium nuclei
D electrons are embedded in the atom

Answer:whole of the positive charge is concentrated at the centre of atom

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