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

Answer

Answer: (d) 0

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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

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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

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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

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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

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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

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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

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

Answer

Answer: (a) radioactivity

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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

Answer

Answer: (c) Roengton

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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

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

Answer

Answer: (b) 10¹⁷

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

Answer

Answer: (d) Co⁶⁰

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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%

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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

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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

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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

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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

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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

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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

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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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