Check the below NCERT MCQ Questions for Class 12 Physics Chapter 13 Nuclei with Answers Pdf free download. MCQ Questions for Class 12 Physics with Answers were prepared based on the latest exam pattern. We have provided Nuclei Class 12 Physics MCQs Questions with Answers to help students understand the concept very well.

Nuclei Class 12 MCQs Questions with Answers

Question 1.
How many electrons are contained in \(_{92}^{238}\)U nucleus?
(a) 92
(b) 146
(c) 238
(d) 0

Answer

Answer: (d) 0


Question 2.
Chadwick was awarded the Nobel prize in Physics in 1935 for his discovery of:
(a) electron
(b) proton
(c) neutron
(d) None of these

Answer

Answer: (c) neutron


Question 3.
The density of a nucleus is of the order of:
(a) 1015 kg m-3
(b) 1018 kg m-3
(c) 1017 kg m-3
(d) 1016 kg m-3

Answer

Answer: (c) 1017 kg m-3


Question 4.
In the given reaction:
\(_{Z}^{A}\)X → \(_{Z+1}^{A}\) Y → \(_{Z-1}^{A-4}\) K → \(_{Z-1}^{A-4}\) K radioactive radiations are emitted in the sequence
(a) α, β, γ
(b) β, α, γ
(c) γ, α, β
(d) β, γ, α

Answer

Answer: (b) β, α, γ


Question 5.
When the mass of a sample of a radioactive substance decreases, the mean life of the sample:
(a) increases
(b) decreases
(c) remain unchanged
(d) first decreases then increases

Answer

Answer: (c) remain unchanged


Question 6.
Alpha particle emitted from a radioactive material are:
(a) Helium nuclei
(b) Hydrogen nuclei
(c) Lithium nuclei
(d) None of the above

Answer

Answer: (a) Helium nuclei


Question 7.
The half life of a radioactive decay is n times its mean life, n is equal to:
(a) 0.6930
(b) 0.0693
(c) \(\frac{1}{0.6930}\)
(d) 0.3070

Answer

Answer: (a) 0.6930


Question 8.
Rutherford is the unit of:
(a) radioactivity
(b) energy
(c) photoelectric current
(d) magnetic field

Answer

Answer: (a) radioactivity


Question 9.
According to Yukawa’s theory of nuclear forces, the origin of nuclear force between nucleons is due to the exchange of
(a) mesons
(b) photons
(c) electrons
(d) positrons

Answer

Answer: (b) photons


Question 10.
An electron and a positron each having a mass equivalent to 0.53 MeV annihilate each other and produce a photon. The minimum energy of the photon is.
(a) 0.53 MeV
(b) 1.06 MeV
(c) 2.12 MeV
(d) zero

Answer

Answer: (b) 1.06 MeV


Question 11.
The wavelength of y-rays is of the order of:
(a) 10-8 m
(b) 10-5 m
(c) 10-11 m
(d) 10-22 m

Answer

Answer: (c) 10-11 m


Question 12.
Radius of 1st Bohr orbit is a0 (= 0.529 Å) What is the radius of 2nd Bohr orbit?
(a) 10-8
(b) 2a0
(c) 4a0
(d) 2√2a0

Answer

Answer: (c) 4a0


Question 13.
The ground state energy of Hydrogen atom is -13.6 eV. What is the potential energy of electron in this state?
(a) 0 eV
(b) -13.6 eV
(c) 2 eV
(d) -27.2 eV

Answer

Answer: (d) -27.2 eV


Question 14.
Which of the following atoms has the lowest ionization potential?
(a) \(_{8}^{8}\)O
(b) \(_{7}^{14}\)N
(c) \(_{55}^{133}\)Cs
(d) \(_{18}^{40}\)Ar

Answer

Answer: (c) \(_{55}^{133}\)Cs


Question 15.
The Bohr model of atom:
(a) assumes that the angular momentum of electron is quantized
(b) uses Einstein’s photoelectric equation
(c) predicts continuous emission spectra for atoms
(d) predicts the same emission spectra for all types of atoms

Answer

Answer: (a) assumes that the angular momentum of electron is quantized


Question 16.
Nuclear force is:
(a) strong, short range and charge independent force
(b) charge independent, attractive and long range force
(c) strong, charge dependent and short range attractive force
(d) long range, change dependent and attractive force

Answer

Answer: (a) strong, short range and charge independent force


Question 17.
If radio active nuclei emits β-particle, then mass-number:
(a) increased by 1 unit
(b) decreases by 1 unit
(c) increases by 2 unit
(d) decreases by 2 unit

Answer

Answer: (a) increased by 1 unit


Question 18.
An alpha particle is emitted from \(_{88}\)Ra\(^{226}\), then the product nuclei has:
(a) Z = 84, A = 224
(b) Z = 86, A = 224
(c) Z = 86, A = 222
(d) Z = 82, A = 222

Answer

Answer: (c) Z = 86, A = 222


Question 19.
X-ray was discovered by :
(a) Becqueral
(b) Marie curie
(c) Roengton
(d) Vanlaw

Answer

Answer: (c) Roengton


Question 20.
Fusion takes place at high temperature because:
(a) Atom are ionised at high temperature
(b) Molecules break up at high temperature
(c) Nuclei break up at high temp.
(d) Kinetic energy is high enough to overcome repulsion between nuclei

Answer

Answer: (d) Kinetic energy is high enough to overcome repulsion between nuclei


Question 21.
The order of nuclear density is :
(a) 103
(b) 1017
(c) 106
(d) None

Answer

Answer: (b) 1017


Question 22.
The isotope generally used for the treatment of cancer is:
(a) I131
(b) Hg197
(c) O15
(d) Co60

Answer

Answer: (d) Co60


Question 23.
What percentage of radioactive substance is left after 5 half lives?
(a) 3.125%
(b) 6.25%
(c) 12.33%
(d) 31%

Answer

Answer: (a) 3.125%


Question 24.
Mass is converted into energy according to the relation:
(a) E = me²
(b) E = mgh
(c) E = \(\frac{3}{2}\)me²
(d) E = \(\frac{mgH}{c^2}\)

Answer

Answer: (a) E = me²


Question 25.
The helium atom does not contain
(a) two protons
(b) two electrons
(c) two neutrons
(d) six nucleons

Answer

Answer: (d) six nucleons


Question 26.
The more readily fissionable isotope of uranium has an atomic mass of:
(a) 234
(b) 235
(c) 236
(d) 238

Answer

Answer: (b) 235


Question 27.
Energy of electron in the 1st orbit of H-atom is:
(a) -13.6 MeV
(b) -13.6 eV
(c) -13.6 J
(d) 13.6 J

Answer

Answer: (b) -13.6 eV


Question 28.
The mass no. of a nucleus is M and its atomic no. is Z. The number of neutrons in the nucleus is :
(a) M – Z
(b) M
(c) Z
(d) M + Z

Answer

Answer: (a) M – Z


Question 29.
The phenomena of radioactivity is:
(a) Exothermic change with increase or decrease with temperature
(b) increases on applied pressure
(c) nuclear process does not depend on external factors
(d) None of these

Answer

Answer: (c) nuclear process does not depend on external factors


Question 30.
When one gm of mass is converted into energy, it is equal to:
(a) 103 kWh
(b)109 kWh
(c) 1010 kWh
(d) 1011 kWh

Answer

Answer: (a) 103 kWh


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