NCERT Solutions for class 12 Physics | Chapter 12 - Atoms

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Questions
1 The Bohr model of atoms
A assumes that the angular momentum of elec-trons is quantized.
B uses Einstein’s photoelectric equation.
C predicts continuous emission spectra for at-oms.
D predicts the same emission spectra for all types of atoms.

Answer:assumes that the angular momentum of elec-trons is quantized.
2 The first spectral series was discovered by
A Balmer
B Lyman
C Paschen
D Pfund

Answer:Balmer
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3 In the Geiger-Marsden scattering experiment the number of scattered particles detected are maximum and minimum at the scattering angles respectively at
A 0° and 180°
B 180° and 0°
C 90° and 180°
D 45° and 90°

Answer:0° and 180°
4 Which of the following spectral series falls within the visible range of electromagnetic radiation?
A Lyman series
B Balmer series
C Paschen seriee
D Pfund series

Answer:Balmer series
5 In Geiger-Marsden scattering experiment, the trajectory traced by an a-particle depends on
A number of collision
B number of scattered a-particles
C impact parameter
D none of these

Answer:impact parameter
6 Which of the following postulates of the Bohr model led to the quantization of energy of the hydrogen atom?
A The electron goes around the nucleus in circular orbits.
B The angular momentum of the electron can only be an integral multiple of h/2π.
C The magnitude of the linear momentum of the electron is quantized.
D Quantization of energy is itself a postulate of the Bohr model.

Answer:The angular momentum of the electron can only be an integral multiple of h/2π.
7 If the radius of inner most electronic orbit of a hydrogen atom is 5.3 * 10~n m, then the radii of n = 2 orbits is
A 1.12 Å
B 2.12 Å
C 3.22 Å
D 4.54 Å

Answer:2.12 Å
8 In the Geiger-Marsden scattering experiment, is case of head-on collision the impact parameter should be
A maximum
B minimum
C infinite
D zero

Answer:maximum
9 The first model of atom in 1898 was proposed by
A Ernst Rutherford
B Albert Einstein
C J.J. Thomson
D Niels Bohr

Answer:J.J. Thomson
10 The diagram shows the energy levels for an electron in a certain atom. Which transition shown represents the emission of a photon with the most energy?

Class 12 Physics Chapter 12 Atoms

A I
B II
C III
D IV

Answer:III
11 The total energy that will be released if a nucleus is built from its constituents is called the:
A binding energy of the nucleus
B binding energy of the solid
C binding energy of the atom
D None of these

Answer:binding energy of the nucleus
12 Natural radioactivity was discovered by:
A Joliot
B Becquerel
C Pauli
D None of these

Answer:Becquerel
13 The energy equivalent to mass defect is called :
A binding energy
B internal energy
C external energy
D enthalpy

Answer:binding energy
14 P-decay produces:
A isobars
B isotopes
C isotones
D All the above

Answer:isobars
15 Transmutation of nuclei was discovered by:
A Rutherford
B Becquerel
C Pauli
D None of these

Answer:Rutherford
16 For ionization of excited Hydrogen atom, the, required energy is:
A a little less than 13.6
B equal to 13.6
C more than 13.6
D 3.4 or less

Answer:3.4 or less
17 The concept of electron spin was introduced by:
A Becquerel
B Goudsmit
C Millikan
D Uhlenbeek and Goudsmit

Answer:Uhlenbeek and Goudsmit
18 The mass of a neutron is:
A 1.00866 u
B 1.0866 u
C 1.866 u
D 0.1866 u

Answer:1.00866 u
19 The energy equivalent to one atomic mass unit is :
A 1.6 × 10-19 J
B 6.02 × 1023 J
C 9.31 MeV
D 931 MeV

Answer:931 MeV
20 Half-life of a substance depends on:
A pressure
B temperature
C density
D None of these

Answer:None of these

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