JEE Questions for Physics Atoms And Nuclei Quiz 5 - MCQExams.com

Which of the following is not conserved n nuclear reaction?
  • Total energy
  • Mass number
  • Charge number
  • Number of fundamental particles
The number of α - particles and β - particles respectively. emitted in the reaction 88A196 →78B164 are
  • 8 and 8
  • 8 and 6
  • 6 and 8
  • 6 and 6
The radius of a nucleus with atomic mass number 7 is 2 Fm. Find the radius of nucleus with atomic number 189.
  • 3 Fm
  • 4 Fm
  • 5 Fm
  • 6 Fm
As mass number increases, surface area
  • decreases
  • increases
  • remains the same
  • remains the same and increases
7N14 is bombarded with 2He4. The resulting nucleus is 8O17 with the emission of
  • neutrino
  • anti - neutrino
  • proton
  • neutron

Physics-Atoms and Nuclei-62577.png
  • 28.24 MeV
  • 17.28 MeV
  • 1.46 MeV
  • 39.2 MeV
Calculate the energy released when three α-particles combined to form a 12C C nucleus, the mass defect is (atomic mass of 2He4 is 4.002603 u)
  • 0.007809 u
  • 0.002603 u
  • 4.002603u
  • 0.5u
If M is the atomic mass and A is the mass number, packing fraction is given by

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  • 2)
    Physics-Atoms and Nuclei-62579.png

  • Physics-Atoms and Nuclei-62580.png

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If 92U238 emits 8 α – particles and 6 β – particles, then the resulting nucleus is
  • 82U206
  • 82Pb206
  • 82U210
  • 82U214
If a star can convert all the He nuclei completely into oxygen nuclei, the energy released per oxygen nuclei is (mass of the nucleus is 4.0026 amu and mass of oxygen nucleus is 15.9994 amu)
  • 7.6 MeV
  • 56.12 MeV
  • 10.24 MeV
  • 23.9 MeV

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  • 2)
    Physics-Atoms and Nuclei-62586.png

  • Physics-Atoms and Nuclei-62587.png

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Two nucleons are at a separation of one Fermi. Protons have a charge of + 1.6 × 10-19 C. The net nuclear force between them is F1, if both are neutrons, F2 if both are protons and F3 if one is proton and other is neutron
  • F1 = F2 > F3
  • F1 = F2 = F3
  • F1 < F2 < F3
  • F1 > F2 > F3
The activity of a radioactive sample is measured as No counts per minute at t = 0 and No/C counts per minute at t = 5 min. The time, (in minute) at which the activity reduces to half its value, is
  • loge (2/5)
  • 5/loge 2
  • 5 log10 2
  • 5 loge 2
Given a sample of radium -226 having half-life of 4 days. Find, the probability, a nucleus disintegrates after 2 half lifes.
  • 1
  • 1/2
  • 1.5
  • 3/4
The relation between half - life (T) and decay constant (λ) is
  • λT = 1
  • λT = 1/2
  • λT = loge 2
  • λ = log.2T
For the radioactive nuclei that undergo either α or β decay, which one of the following cannot occur?
  • Isobar of original nucleus is produced
  • Isotope of original nucleus is produced
  • Nuclei with higher atomic number that of the original nucleus is produced
  • Nuclei with lower atomic number than that of the original nucleus is produced
In a radioactive disintegration, the ratio of initial number of atoms to the number of atoms present at an instant of time equal to its mean life is
  • 1/e2
  • 1/e
  • e
  • e2
The β -decay process, discovered around 1900, is basically the decay of a neutron (n). In the laboratory, a proton (p) and an electron (e- ) are observed as the decay products of the neutron. Therefore, considering the decay of a neutron as a two body decay process, it was predicted theoretically that the kinetic energy of the electron should be a constant. But experimentally, it was observed that the electron kinetic energy has a continuous spectrum. Considering a three body decay process, i.e. n → p + e- + ve around 1930, Pauli explained the observed electron energy spectrum. Assuming the anti-neutrino (v ̅e) to be mass-less and possessing negligible energy, and the neutron to be at rest, momentum and energy conservation principles are applied. From this calculation, the maximum kinetic energy carried by the proton is 0.8 × 106 eV. The Kinetic energy of the electron is only the recoil energy.
What is the maximum energy of the anti-neutrino?
  • zero
  • Much less that 0.8 × 106 eV
  • Nearly 0.8 × 106 eV
  • Much larger tan 0.8 × 106 eV
The β -decay process, discovered around 1900, is basically the decay of a neutron (n). In the laboratory, a proton (p) and an electron (e- ) are observed as the decay products of the neutron. Therefore, considering the decay of a neutron as a two body decay process, it was predicted theoretically that the kinetic energy of the electron should be a constant. But experimentally, it was observed that the electron kinetic energy has a continuous spectrum. Considering a three body decay process, i.e. n → p + e- + ve around 1930, Pauli explained the observed electron energy spectrum. Assuming the anti-neutrino (v ̅e) to be mass-less and possessing negligible energy, and the neutron to be at rest, momentum and energy conservation principles are applied. From this calculation, the maximum kinetic energy carried by the proton is 0.8 × 106 eV. The Kinetic energy of the electron is only the recoil energy.
A radioactive element has half-life period of 600 yr. After 3000 yr, what amount will remain?
  • 1/2
  • 1/16
  • 1/8
  • 1/32
The β -decay process, discovered around 1900, is basically the decay of a neutron (n). In the laboratory, a proton (p) and an electron (e- ) are observed as the decay products of the neutron. Therefore, considering the decay of a neutron as a two body decay process, it was predicted theoretically that the kinetic energy of the electron should be a constant. But experimentally, it was observed that the electron kinetic energy has a continuous spectrum. Considering a three body decay process, i.e. n → p + e- + ve around 1930, Pauli explained the observed electron energy spectrum. Assuming the anti-neutrino (v ̅e) to be mass-less and possessing negligible energy, and the neutron to be at rest, momentum and energy conservation principles are applied. From this calculation, the maximum kinetic energy carried by the proton is 0.8 × 106 eV. The Kinetic energy of the electron is only the recoil energy.
A radioactive substance decays at the rate 5000 disintegration per minute. After 5 mins, it disintegrates at 1250 disintegration per min. The decay constant
  • 0.4 ln 2 min-1
  • 0.5 ln 3 min-1
  • 0.5 ln 2min-2
  • 0.2 ln 2 min-1
The half of a radioactive substance is 20 min. The approximate time interval (t2 – t1) between the time t2 when 2/3 of it has decayed and time t1 when 1/3 of it had decayed is
  • 14 min
  • 20 min
  • 28 min
  • 7 min
The fraction of the initial number of radioactive nuclei which remain undecayed after half of a half-life of the radioactive sample is
  • 1/√2
  • 1/2
  • 1/2√2
  • 1/4

Physics-Atoms and Nuclei-62593.png
  • 8
  • 7
  • 4
  • 8.5
A radioactive nucleus (initial mass number A and atomic number Z) emits 3 a-particles and 2 positrons. The ratio of number of neutrons to that of protons in the final nucleus will he

  • Physics-Atoms and Nuclei-62595.png
  • 2)
    Physics-Atoms and Nuclei-62596.png

  • Physics-Atoms and Nuclei-62597.png

  • Physics-Atoms and Nuclei-62598.png
β - decay means emission of electron from
  • innermost electron orbit
  • a stable nucleus
  • outermost electron orbit
  • radioactive nucleus
The activity of a radioactive element decreases to one-third of the original activity Ao in a period of 9 yr. After a further lapes of 9 yr, its activity will be
  • Ao
  • 2/3 Ao
  • Ao/9
  • Ao/6
  • Ao/18
In β+ decay process, the following changes take place inside the nucleus

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    Physics-Atoms and Nuclei-62600.png

  • Physics-Atoms and Nuclei-62601.png

  • Physics-Atoms and Nuclei-62602.png
Neutrino emission in β-decay was predicted theoretically by
  • Planck
  • Heisenberg
  • Laue
  • Pauli
Consider α - particles, β - particles and γ - rays, each having an energy of 0.5 MeV. In increasing order of penetrating powers, the radiations are
  • α, β, and γ
  • α, γ, and β
  • β, γ and α
  • γ, β, and α
Half-life of radioactive sample, when activity of material initially was 8 counts and after 3 h it becomes 1 count, is
  • 2 h
  • 1 h
  • 3 h
  • 4 h
Which shows radioactivity?
  • Protium
  • Deuterium
  • Tritium
  • None of these

Physics-Atoms and Nuclei-62604.png
  • one electron and one neutron
  • one neutron and one electron
  • one α- particle and one neutron
  • one α- particle and one electron
The end product of the decay of 90Th232 is 82Pb208. The number of α and β - particles emitted are respectively
  • 6, 4
  • 3, 3
  • 4, 6
  • 6, 0
The radioactivity of a certain material drops to 1/16 of the initial value in 2 h. The half - life of this radio nuclide is
  • 10 min
  • 20 min
  • 30 min
  • 40 min
Half-life of radioactive substance is 3.20 h. What is the time taken for a 75% of substance to he used?
  • 6.38 h
  • 12 h
  • 4.18 day
  • 1.2 day
Select the wrong statement.
  • Radioactivity is a statistical process
  • Radioactivity is a spontaneous process.
  • Radioactivity is neutral characteristic of few elements.
  • Radioactive elements cannot be produced in the laboratory.

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  • 2)
    Physics-Atoms and Nuclei-62608.png

  • Physics-Atoms and Nuclei-62609.png

  • Physics-Atoms and Nuclei-62610.png
The fossil bone has a 14C : 12C ratio, which is [1/16] of that in a living animal bone. If the half - life of 14C is 5730 yr, then the age of the fossil bone is
  • 11460 yr
  • 17190 yr
  • 22920 yr
  • 45840 yr
In radioactive decay process, the negatively charged emitted β- particles are
  • the electrons present inside the nucleus
  • the electrons produced as a result of the decay of neutrons inside the nucleus
  • the electrons produced as a result of collisions between atoms
  • the electrons orbiting around the nucleus
We have seen that a γ - ray dose of 3 qy is lethal to half the people exposed to it. If the equivalent energy were absorbed as heat, what rise in body temperature would result ?
  • 300 μK
  • 700 μK
  • 455 μK
  • 390 μK
Mass spectrometric analysis of potassium and argon atoms in a moon rock sample shows that the ratio of the number of (stable) 40Ar atoms presents to the number of (radioactive) 40K atoms is 10.3. Assume that all the argon atoms were produced by the decay of potassium atoms, with a half - life of 1.25 × 109 yr. How old is the rock?
  • 2.95 × 1011 yr
  • 2.95 × 109 yr
  • 4.37 × 109 yr
  • 4.37 × 1011 yr
The half-life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially they have the same number of atoms. Then
  • X will decay faster than Y
  • Y will decay faster than X
  • Y and X have same decay rate initially
  • X and Y decay at same rate always
A and B are two radioactive substances whose half-lifes are 1 and 2 yr, respectively. Initially 10 g of A and 1 g of B is taken. The time (approximate) after which they will have same quantity remaining is
  • 6.62 yr
  • 5 yr
  • 3.2 yr
  • 7 yr
Ionisation power and penetration range of radioactive radiation increases in the order
  • γ, β, α and γ, β, α respectively
  • γ, β, α and α, β, γ respectively
  • α, β, γ and α, β, γ respectively
  • α, β, γ and γ, β, α respectively
The half-life of a radioactive element is 3.8 days. The fraction left after 19 days will be
  • 0.124
  • 0.062
  • 0.093
  • 0.031
Radio carbon dating is done by estimating in specimen the
  • amount of ordinary carbon still present
  • amount of radio carbon still present
  • ratio amount of 14C6 to 12C6 still present
  • ratio of amount of 12C6 to 14C6 still present
In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. if the decay constant of the material is λ, then
  • R1 = R2 e-λ(t1-t2)
  • R1 = R2 eλ(t1-t2)
  • R1 = R2 (t2/t1)
  • R1 = R2
Which of the following cannot be emitted by radioactive substances during their decay ?
  • Protons
  • Neutrinos
  • Helium nuclei
  • Electrons
A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is
  • 7070
  • 9000
  • 8000
  • 7500
Radium has a half-life of 5 yr. The probability of decay of a radium nucleus in 10 yr is
  • 50%
  • 75%
  • 100%
  • 60%
  • 25%
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