JEE Physics Nuclei MCQs Set A

Question: The nuclear radius as compared to the atomic radius is of the order

• a) 10^–5
• b) 10^–7
• c) 10^–9
• d) 10^–3

Answer: 10^–5

Question: Two nuclei which are not identical but have the same number of nucleons represent

• a) Isobars
• b) IsotonesIsotopes
• c) Isotopes
• d) Isotones

Answer: Isobars

Question:  In a nuclear fusion reaction, if the energy is released then

• a)

  

• b)

  

• c)

  

• d)

  Mass of product > Mass of reactant

Answer:

Question:

• a) 7.675 MeV
• b) 0 MeV
• c) 3.675 MeV
• d) 2.675 MeV

Answer: 7.675 MeV

Question: Which of the following pairs of particles cannot exert nuclear force on each other?

• a) All of these
• b) Electron and neutron
• c) Neutron and electron
• d) Proton and electron

Answer: All of these

Question: When two nuclei of mass X and Y respectively fuse to form a nucleus of mass m alongwith the liberation of some energy, then

• a) X + Y > m
• b) X – Y = m
• c) X + Y = m
• d) X + Y < m

Answer: X + Y > m

Question: The nuclear force between two nucleons is explained by

• a) Meson exchange theory
• b) Gravitation exchange theory
• c) Quark exchange theory
• d) Photon exchange theory

Answer: Meson exchange theory

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 12.13 MeV
• b) 13.018 MeV
• c) 12.13 eV
• d) 0.013018 MeV

Answer: 12.13 MeV

Question: Nuclear energy is released in fusion reaction, since binding energy per nucleon is

• a) Larger for fusion products than for fusing nuclei
• b) Smaller of fusion products than for fusing nuclei
• c) Same for fusion products as for fusing nuclei
• d) Sometimes larger and sometimes smaller

Answer: Larger for fusion products than for fusing nuclei

Question:

• a) X and Z are isotopes
• b) X and Y are isobars
• c) X and Z are isobars
• d) X and Y are isotopes

Answer:  X and Z are isotopes

Question:

• a) 160 MeV
• b) 110 MeV
• c) 90 MeV
• d) 200 MeV

Answer: 160 MeV

Question:

• a) Isotones
• b) Isobars
• c) Isotopes of carbon
• d) Isotopes of nitrogen

Answer: Isotones

Question:

• a) 1.50
• b) 2.750
• c) 3.375
• d) 1.40

Answer:  1.50

Question:

• a) 78
• b) 82
• c) 76
• d) 74

Answer: 78

Question: In nuclear reactions we have the conservation of

• a) Charge, total energy and momentum
• b) Energy only
• c) Mass only
• d) Momentum only

Answer: Charge, total energy and momentum

Question:

• a) Electrostatic repulsion dominate over nuclear attraction
• b) Nuclear repulsion dominate over nuclear attraction
• c) Nuclear force is long range force
• d) Nuclear forces are absent in heavy nucleus

Answer: Electrostatic repulsion dominate over nuclear attraction

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: In the radioactive decay of an element it is found that the count rate reduces from 1024 to 128 in 3 minutes. Its half life will be

• a) 1 minute
• b) 2 minute
• c) 3 minute
• d) 5 minute

Answer: 1 minute

Question: If a radioactive material remains 25% after 16 days, then its half life will be

• a) 8 days
• b) 64 days
• c) 28 days
• d) 32 days

Answer: 8 days

Question: The count rate of a radioactive source at t = 0 was 1600 count/s and at t = 8 s, it was 100 count/s. The count rate (in counts) at t = 6 s was

• a) 200
• b) 300
• c) 400
• d) 150

Answer: 200

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A radioactive sample at any instant has its disintegration rate 5000 disintegrations per minute. After 5 minute, the rate is 1250 disintegrations per minute. The decay constant (per minute) is

• a) 0.4 ln 2
• b) 0.2 ln 2
• c) 0.1 ln 2
• d) 0.8 ln 2

Answer: 0.4 ln 2

Question:  At time t = 0 some radioactive gas is injected into a sealed vessel. At time T some more of the gas is injected into the vessel. Which one of the following graphs best represents the logarithm of the activity A of the gas with time t?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 4.11 × 10⁹ year
• b) 2.74 × 10⁹ year
• c) 5.48 × 10⁹ year
• d) 1.37 × 10⁹ year

Answer: 4.11 × 10⁹ year

Question:

• a) 0.5
• b) 2.0
• c) 3.0
• d) None of these

Answer: 0.5

Question:  In a radioactive decay let N be the number of residual active nuclei, D the number of daughter nuclei, R the rate of decay and M the mass of active sample at any time t. Below are shown four curves

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A freshly-prepared radioactive source of half-life 2 h emits radiation of intensity which is 64 times the permissible safe level. The minimum time after which it would be possible to work safely with this source is

• a) 12 h
• b) 6 h
• c) 24 h
• d) 128 h

Answer: 12 h

Question:

• a) Energy is released due to de-excitation of nucleus
• b) None of these
• c) Energy is released due to conversion of neutron into proton
• d) Pair annihilation takes place

Answer: Energy is released due to de-excitation of nucleus

Question: The sample of a radioactive substance has 10⁶ nuclei. Its half life is 20 s. The number of nuclei that will be left after 10 s is nearly

• a) 7 × 10⁵
• b) 11 × 10⁵
• c) 2 × 10⁵
• d) 1 × 10⁵

Answer:  7 × 10⁵

Question: Half life of radioactive element depends upon

• a) The nature of the element
• b) Temperature
• c) Pressure
• d) Amount of element present

Answer: The nature of the element

Question: Neutrino is a particle which

• a) Has no charge but has spin
• b) Has no charge and no spin
• c) Is charged like an electron and has spin
• d) Has no charge but has mass nearly equal to that of a proton

Answer: Has no charge but has spin

Question: Heavy water instead of ordinary water is used as a moderator in nuclear reactor because ordinary water

• a) Absorbs neutrons
• b) Accelerates neutron
• c) Cannot slow down neutron
• d) Is expensive

Answer: Absorbs neutrons

Question: Out of the following, which one is not emitted by a natural radioactive substance?

• a) Neutrons
• b) Helium nuclei with charge equal to that of two protons
• c) Electromagnetic radiations
• d) Electrons

Answer: Neutrons

Question:

• a) 3.1 × 10¹³
• b) 1.3 × 10¹⁶
• c) 1.3 × 10¹⁵
• d) 3.1 × 10¹⁶

Answer: 3.1 × 10¹³

Question: If 1 g hydrogen is converted into 0.993 gm of helium in a thermonuclear reaction, the energy released in the reaction is

• a) 63 × 10¹⁰ J
• b) 63 × 10¹⁴ J
• c) 63 × 10²⁰ J
• d) 63 × 10⁷ J

Answer: 63 × 10¹⁰ J

Question: Thermal neutrons are those whose energy is about

• a) 0.03 eV
• b) 1 MeV
• c) 0.03 MeV
• d) 1 J

Answer: 0.03 eV

Question:

• a) 3-neutron
• b)

  

• c) 1-neutron
• d)

  

Answer: 3-neutron  

Question: Control rods used in nuclear reactors are made of

• a) Cadmium
• b) Plutonium
• c) Graphite
• d) Stainless steel

Answer: Cadmium

Question:

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: After 3 hours, only 0.25 mg of a pure radioactive material is left. If initial mass was 2 mg then the half life of the substance is

• a) 1 hr
• b) 0.5 hr
• c) 2 hr
• d) 1.5 hr

Answer: 1 hr

Question:

• a) Continuous energy distribution of positrons
• b) Conservation of mass-energy
• c) Conservation of linear momentum
• d) All of these

Answer: Continuous energy distribution of positrons

Question: If a heavy nucleus has N/Z ratio higher than that required for stability, then

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 24 years
• b) 29 years
• c) 64 years
• d) 12 years

Answer: 24 years

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Choose the correct statement

• a) The nuclear force becomes weak if the nucleus contains a large number of nucleons
• b) Nuclei with atomic number less than 82 shows a tendency to disintegrate
• c) The nuclear force becomes strong if the nucleus contains too many neutrons compared to protons
• d) The nuclear force becomes strong if the nucleus contains too many protons compared to neutrons

Answer: The nuclear force becomes weak if the nucleus contains a large number of nucleons

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Ten percent of a radioactive sample has decayed in 1 day. After 2 days, the decayed percentage of nuclei will be

• a) 19%
• b) 20%
• c) 100%
• d) 81%

Answer: 19%

Question: Sample of radioactive element has a mass of 10 gm at an instant t = 0. The approximate mass of this element in the sample after two mean lives is

• a) 1.35 gm
• b) 6.30 gm
• c) 3.70 gm
• d) 2.50 gm

Answer: 1.35 gm

Question: During mean life of a radioactive element, the fraction that disintegrates is

• a)

  

• b)

  

• c)

  

• d) e

Answer:

Question:

• a) A and C are isotopes
• b) A and B are isotopes
• c) A and C are isobars
• d) A and B are isobars

Answer: A and C are isotopes

Question: After five half lives percentage of original radioactive atoms left is

• a) 3.125%
• b) 0.2%
• c) 0.3%
• d) 1%

Answer: 3.125%

Question:

• a) 5 seconds
• b) 7.5 seconds
• c) 15 seconds
• d) 8 seconds

Answer:  5 seconds

Question:

• a) 2.3 × 10⁸ atom/s
• b) 3.2 × 10⁸ atom/s
• c) 2.3 × 10¹¹ atom/s
• d) 3.2 × 10¹¹ atom/s

Answer: 2.3 × 10⁸ atom/s

Question: The average binding energy per nucleon in the nucleus of atom is approximately

• a) 8 MeV
• b) 8 MeV
• c) 8 KeV
• d) 8 J

Answer: 8 MeV

Question:

• a) –10^–16 J
• b) –10^–14 J
• c) –10^–12 J
• d) –10^–10 J

Answer: –10^–16 J

Question:

• a) 11 MeV
• b) 11.1 MeV
• c) 10.9 MeV
• d) 10.8 MeV

Answer: 11 MeV

Question:

Radioactive nuclei P and Q disintegrate into R with half lives 1 month and 2 months respectively. At time t = 0, number of nuclei of each P and Q is x. Time at which rate of disintegration of P and Q are equal, number of nuclei of R is

• a) 1.25 x
• b) 1.5 x
• c) 1.75 x
• d) x

Answer: 1.25 x

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer: