JEE Questions for Physics Atoms And Nuclei Quiz 13 - MCQExams.com

99% of a radioactive element will decay between
  • 6 and 7 half lives
  • 7 and 8 half lives
  • 8 and 9 half lives
  • 9 half lives
The masses of two radioactive substances are same and their half lives are 1 year and 2 years respectively. The ratio of their activities after 6 years will be
  • 1 : 3
  • 1 : 6
  • 1 : 4
  • 1 : 2
In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life
  • 69.3%
  • 63%
  • 50%
  • 37%
The S.I. unit of radioactivity is
  • Roentgen
  • Rutherford
  • Curie
  • Becquerel
Half-life of a substance is 10 years. In what time, it becomes 1/4 th part of the initial amount
  • 5 years
  • 10 years
  • 20 years
  • None of these
If N0 is the original mass of the substance of half-life period T1/2 = 5 years, then the amount of substance left after 15 years is
  • N0/8
  • N0/16
  • N0/2
  • N0/4
The half-life of a radioactive substance is 48 hours. How much time will it take to disintegrate to its 1/16 th part
  • 12 h
  • 16 h
  • 48 h
  • 192 h
Which of the following radiations has the least wavelength
  • X–rays
  • γ–rays
  • β–rays
  • α–rays
A nucleus with Z = 92 emits the following in a sequence; α, β–, β–, α, α, α, α, α, β–, β–, α, β+, β+, α. The Z of the resulting nucleus is
  • 74
  • 76
  • 78
  • 82
A radioactive material has a half-life of 8 years. The activity of the material will decrease to about 1/8 of its original value in
  • 256 years
  • 128 years
  • 64 years
  • 24 years
Mean life of a radioactive sample is 100 seconds. Then its half life (in minutes) is
  • 0.693
  • 1
  • 10–4
  • 1.155
If half life of radium is 77 days. Its decay constant in day will be
  • 3 × 10–13/day
  • 9 × 10–3/day
  • 1 × 10–3/day
  • 6 × 10–3/day
In a radioactive reaction 92X232 → 22Y204, the number of α–particles emitted is
  • 7
  • 6
  • 5
  • 4
The \'rad\' is the correct unit used to report the measurement of
  • The energy delivered by radiation to a target
  • The biological effect of radiation
  • The rate of decay of a radioactive source
  • The ability of a beam of gamma ray photons to produce ions in a target
A radioactive substance contains 10,000 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
The volume of a nucleus is directly proportional to
(where A = mass number of the nucleus)
  • A
  • A3
  • √A
  • A1/3

Physics-Atoms and Nuclei-62996.png
  • 3 : 58
  • 58 : 3
  • 1 : 58
  • 58 : 1
80 kg of a radioactive material reduces to 10 kg in one hour. The decay constant of the material is
  • 5.80 × 10–4S–1
  • 1.16 × 10–3S–1
  • 2.32 × 10–3S–1
  • 4.64 × 10–3S–1

Physics-Atoms and Nuclei-62999.png
  • 2 : 1
  • 1 : 2
  • 1 : 4
  • 1 : 16
  • 4 : 1
An α–particle of 5 MeV energy strikes with a nucleus of uranium at stationary at an scattering angle of 180°. The nearest distance upto which α–particle reaches the nucleus will be of the order of
  • 1 Å
  • 10–10cm
  • 10–12 cm
  • 10–15 cm
The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is
  • 1/2
  • 2/137
  • 1/137
  • 1/237
Kα and Kβ, X-rays are emitted when there is a transition of electron between the levels
  • n = 2 to n = 1 and n = 3 to n = 1 respectively
  • n = 2 to n =1 and n = 3 to n = 2 respectively
  • n = 3 to n = 2 and n = 4 to n = 2 respectively
  • n = 3 to n = 2 and n = 4 to n = 3 respectively
An energy of 24.6 eV is required to remove one of the electrons from a neutral helium atom. The energy (in eV) required to remove both the electrons from a neutral helium atom is
  • 79.0
  • 51.8
  • 49.2
  • 38.2
The number of revolutions per second made by an electron in the first Bohr orbit of hydrogen atom is of the order of
  • 1020
  • 1019
  • 1017
  • 1015
Consider an electron (m = 9.1 × 10–31kg) confined by electrical forces to move between rigid walls separated by 1.0 × 10–9 metre, which is about five atomic diameters. The quantized energy value for the lowest stationary state is
  • 12 × 10–20 J
  • 6.0 × 10–20 J
  • 6.0 × 10–18 J
  • 6 J
α–particles of energy 400 KeV are bombarded on nucleus of 82Pb. In scattering of α–particles, its minimum distance from nucleus will be
  • 0.59 nm
  • 0.59 Å
  • 5.9 pm
  • 0.59 pm
What is the radius of iodine atom (at. no. 53, mass number 126)?
  • 2.5 × 10–11 m
  • 2.5 × 10–9 m
  • 7 × 10–9 m
  • 7 × 10–6 m
If in Rutherford\'s experiment, the number of particles scattered at 90° angle are 28 per min, then number of scattered particles at an angle 60° and 120° will be
  • 112/ min, 12.5/min
  • 100/min, 200/min
  • 50/min, 12.5/min
  • 117/min, 25/min
A double charged lithium atom is equivalent to hydrogen whose atomic number is 3. The wavelength of required radiation for emitting electron from first to third Bohr orbit in Li++ will be (Ionisation energy of hydrogen atom is 13.6 eV)
  • 182.51 Å
  • 177.17 Å
  • 142.25 Å
  • 113.74 Å
The ionisation potential of H–atom is 13.6 V. When it is excited from ground state by monochromatic radiations of 970.6 Å, the number of emission lines will be (according to Bohr\'s theory)
  • 10
  • 8
  • 6
  • 4
A neutron with velocity V strikes a stationary deuterium atom, its kinetic energy changes by a factor of
  • 15/16
  • 1/2
  • 2/1
  • None of these
In the Bohr model of the hydrogen atom, let R, v and E represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is proportional to the quantum number n
  • R /E
  • E /v
  • RE
  • vR
Which of the following atoms has the lowest ionization potential ?

  • Physics-Atoms and Nuclei-63013.png
  • 2)
    Physics-Atoms and Nuclei-63014.png

  • Physics-Atoms and Nuclei-63015.png

  • Physics-Atoms and Nuclei-63016.png

Physics-Atoms and Nuclei-63018.png
  • rn ∝ n
  • rn ∝ 1/n
  • rn ∝ n2
  • rn ∝ 1/n2
If the atom 100Fm257 follows the Bohr model and the radius of 100Fm257 is n times the Bohr radius, then find n
  • 100
  • 200
  • 4
  • 1/4
The binding energy per nucleon of O16 7.97 MeV and that of O17 is 7.75 MeV. The energy (in MeV) required to remove a neutron from O17 is
  • 3.52
  • 3.64
  • 4.23
  • 7.86
The rest energy of an electron is 0.511 MeV. The electron is accelerated from rest to a velocity 0.5 c. The change in its energy will be
  • 0.026 MeV
  • 0.051 MeV
  • 0.079 MeV
  • 0.105 MeV
A heavy nucleus at rest breaks into two fragments which fly off with velocities in the ratio 8 : 1. The ratio of radii of the fragments is
  • 1 : 2
  • 1 : 4
  • 4 : 1
  • 2 : 1
For uranium nucleus how does its mass very with volume
  • m ∝ V
  • m∝1/V
  • m ∝ √V
  • m ∝ V2
The rest mass of an electron as well as that of positron is 0.51 MeV. When an electron and positron are annihilate, they produce gamma-rays of wavelength (s)
  • 0.012 Å
  • 0.024 Å
  • 0.012 Å to ∞
  • 0.024 Å to ∞
A nucleus with mass number 220 initially at rest emits an α–particle. If the Q value of the reaction is 5.5 MeV, calculate the kinetic energy of the α–particle
  • 4.4 MeV
  • 5.4 MeV
  • 5.6 MeV
  • 6.5 MeV
The half life of radioactive Radon is 3.8 days. The time at the end of which 1/20th of the Radon sample will remain undecayed is (Given log10 e = 0.4343)
  • 3.8 days
  • 16.5 days
  • 33 days
  • 76 days
If 10% of a radioactive material decays in 5 days, then the amount of original material left after 20 days is approximately
  • 60%
  • 65%
  • 70%
  • 75%
A radioactive sample S1 having an activity of 5μCi has twice the number of nuclei as another sample S2 which has an activity of 10μCi. The half lives of S1 and S2 can be
  • 20 years and 5 years, respectively
  • 20 years and 10 years, respectively
  • 10 years each
  • 5 years each
The half life period of a radioactive element X is same as the mean life time of another radioactive element Y. Initially both of them have the same number of atoms. Then
  • X and Y have the same decay rate initially
  • X and Y decay at the same rate always
  • Y will decay at a faster rate than X
  • X will decay at a faster rate than Y
For a substance the average life for a-emission is 1620 years and for β emission is 405 years. After how much time the 1/4 of material remains after α and β emission
  • 1500 years
  • 300 years
  • 449 years
  • 810 years
The half-life of radioactive Polonium (Po) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is
  • 2000
  • 3000
  • 4000
  • 5000
A and B are two radioactive substances whose half lives are 1 and 2 years 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 years
  • 5 years
  • 3.2 years
  • 7 years
Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be
  • 20 min
  • 40 min
  • 30 min
  • 25 min
After 280 days, the activity of a radioactive sample is 6000 dps. The activity reduces to 3000 dps after another 140 days. The initial activity of the sample in dps is
  • 6000
  • 9000
  • 3000
  • 24000
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