JEE Questions for Physics Atoms And Nuclei Quiz 12 - MCQExams.com

Which can pass through 20 cm thickness of the steel
  • α - particles
  • β - particles
  • γ - rays
  • Ultraviolet rays
What percentage of original radioactive atoms is left after five half lives
  • 0.3%
  • 1%
  • 31%
  • 3.125%
Alpha rays emitted from a radioactive substance are
  • Negatively charged particles
  • Ionised hydrogen nuclei
  • Doubly ionised helium atom
  • Uncharged particles having the mass equal to proton
Half life of Bi210 is 5 days. If we start with 50,000 atoms of this isotope, the number of atoms left over after 10 days is
  • 5,000
  • 25,000
  • 12,500
  • 20,000
A nucleus of atomic mass A and atomic number Z emits β - particles. The atomic mass and atomic number of the resulting nucleus are
  • A, Z
  • A + 1, Z
  • A, Z + 1
  • A - 4, Z - 2
The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 sec. Its half life is
  • 2 sec
  • 4 sec
  • 5 sec
  • 6 sec
The decay constant λ of the radioactive sample is the probability of decay of an atom in unit time, then
  • λ decreases as atoms become older
  • λ increases as the age of atoms increases
  • λ is independent of the age
  • Behavior of λ with time depends on the nature of the activity
Half life of radioactive element depends upon
  • Amount of element present
  • Temperature
  • Pressure
  • Nature of element
The decay constant of radium is 4.28 × 10–4 per year. Its half life will be
  • 2000 years
  • 1240 years
  • 63 years
  • 1620 years
Half-life of radioactive sample, when activity of material initially was 8 counts and after 3 hours it becomes 1 count, is
  • 2 hr
  • 1 hr
  • 3 hr
  • 4 hr
A sample contains 16 g of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is
  • Less than 1 mg
  • 2)
    Physics-Atoms and Nuclei-62943.png

  • Physics-Atoms and Nuclei-62944.png
  • 1 g
A radio-isotope has a half-life of 5 years. The fraction of the atoms of this material that would decay in 15 years will be
  • 1/8
  • 2/3
  • 7/8
  • 5/8
Three α - particles and one β - particle decaying takes place in series from an isotope 88Ra236. Finally the isotope obtained will be
  • 84X220
  • 86X222
  • 83X224
  • 83X215
A nuclear fusion reaction is given 1H2 + 1H2 → 2He3 + 0n1 + Q (energy). If 2 moles of deuterium are fused, then total released energy is
  • 2Q
  • 4Q
  • Q × 6.02 × 1023
  • Q × 2 × 6 × 1023
If the half life of a radioactive sample is 10 hours, its mean life is
  • 14.4 hr
  • 7.2 hr
  • 20 hr
  • 6.93 hr
If 20 g of a radioactive substance due to radioactive decay reduces to 10 g in 4 min, then in what time 80 g of the same substance will reduce to 10 g
  • In 8 min
  • In 12 min
  • In 16 min
  • In 20 min
16 g sample if a radioactive element is taken from Bombay to Delhi in 2 hour and it was found that 1 g of the element remained (undisintegrated). Half life of the element is
  • 2 hour
  • 1 hour
  • 1/2 hour
  • 1/4 hour
Unit of radioactivity is Rutherford. Its value is
  • 3.7 × 1010 disintegrations/s
  • 3.7 × 106 disintegrations/s
  • 1.0 × 1010 disintegrations/s
  • 1.0 × 106 disintegrations/s
The count rate of a Geiger-Muller counter for the radiation of a radioactive material of half life of 30 minutes decreases to 5 s–1 after 2 hours. The initial count rate was
  • 25s–1
  • 80s–1
  • 625s–1
  • 20s–1
In a radioactive decay, the half-life of radioactive substance is t1/2 = 69.3 sec. The decay constants is
  • 0.01 sec–1
  • 0.1 sec–1
  • 10 sec–1
  • 1 sec–1
An element used for radioactive carbon dating for more than 5600 years is
  • C – 14
  • U – 234
  • U – 238
  • Po – 94
The radioactive nucleus 7N13 decays to 6C13 through the emission of
  • Neutron
  • Proton
  • Electron
  • Positron
The counting rate observed from a radioactive source at t = 0 second was 1600 counts per second and at t = 8 seconds it was 100 counts per second. The counting rate observed, as counts per second at t = 6 seconds, will be
  • 400
  • 300
  • 200
  • 150
In a radioactive decay, neither the atomic number nor the mass number changes. Which of the following would be emitted in the decay process
  • Proton
  • Neutron
  • Electron
  • Photon
The half life period of a radioactive substance is 5 min. The amount of substance decayed in 20 min will be
  • 93.75%
  • 75%
  • 25%
  • 6.25%
22Ne nucleus after absorbing energy decays into two a - particles and an unknown nucleus. the unknown nucleus is
  • Nitrogen
  • Carbon
  • Boron
  • Oxygen
If the radioactive decay constant of radium is 1.07 × 10–4 per year, than its half life period is approximately equal to
  • 8,900 years
  • 7,000 years
  • 6,476 years
  • 2,520 years
Carbon–14 decays with half-life of about 5,800 years. In a sample of bone, the ratio of carbon–14 to carbon –2 is found to be 1/4 of what it is in free air. This bone may belong to a period about x centuries ago, where x is nearest to
  • 2 × 58
  • 58
  • 58/2
  • 3 × 58
Age of a tree is determined using radio-isotope of
  • Carbon
  • Cobalt
  • Iodine
  • Phosphorus
An atom of mass number 15 and atomic number 7 captures an α - particle and then emits a proton. The mass number and atomic number of the resulting product will respectively be
  • 14 and 2
  • 15 and 3
  • 16 and 4
  • 18 and 8
When 3Li7 nuclei are bombarded by protons, and the resultant nuclei are 4Be8, the emitted particles will be
  • Beta particles
  • Gamma photons
  • Neutrons
  • Alpha particles
If half life of a radioactive element is 3 hours, after 9 hours its activity becomes
  • 1/9
  • 1/27
  • 1/6
  • 1/8
A radioactive sample with a half life of 1 month has the label \ Activity =2 micro curies on 1.8.1991.\ What will be its activity two months later
  • 1.0 micro curies
  • 0.5 micro curies
  • 4 micro curie
  • 8 micro curies
An element A decays into element C by a two step process:
A → B + 2He4; B → C + 2e– Then
  • A and C are isotopes
  • A and C are isobars
  • A and B are isotopes
  • A and B are isobars
At any instant the ratio of the amount of radioactive substances is 2 : 1. if their half lives be respectively 12 and 16 hours, then after two days, what will be the ratio of the substances
  • 1 : 1
  • 2 : 1
  • 1 : 2
  • 1 : 4
Which of the following isotopes is used for the treatment of cancer
  • K40
  • Co60
  • Sr90
  • I131
A radio isotope has a half life of 75 years. The fraction of the atoms of this material that would decay in 150 years will be
  • 66.6%
  • 85.5%
  • 62.5%
  • 75%

Physics-Atoms and Nuclei-62967.png

  • Physics-Atoms and Nuclei-62968.png
  • 2)
    Physics-Atoms and Nuclei-62969.png

  • Physics-Atoms and Nuclei-62970.png

  • Physics-Atoms and Nuclei-62971.png
The activity of a sample is 64 × 10–5 Ci. Its half-life is 3 days. The activity will become 5 × 10–6 Ci after
  • 12 days
  • 7 days
  • 18 days
  • 21 days
A nucleus of an element 84X202 emits an α–particle first, a β–particle next and then a gamma photon. The final nucleus formed has an atomic number
  • 200
  • 199
  • 83
  • 198
3.8 days is the half-life period of a sample. After how many days, the sample will become 1/8th of the original substance
  • 11.4
  • 3.8
  • 3
  • None of these
A radioactive substance emits
  • α–rays
  • β–rays
  • γ–rays
  • All of these
The large scale destruction, that would be caused due to the use of nuclear weapons is called
  • Nuclear holocaust
  • Thermo-nuclear reaction
  • Neutron reproduction factor
  • None of the above
Given a sample of Radium-226 having half-life of 4 days. Find the probability, a nucleus isintegrates after 2 half lives
  • 1
  • 1/2
  • 1.5
  • 3/4
A radioactive sample has half-life of 5 years. Probability of decay in 10 years will be
  • 100%
  • 75%
  • 50%
  • 25%

Physics-Atoms and Nuclei-62978.png
  • A – 3, A – 4
  • Z – 1, A – 4
  • Z – 2, A – 4
  • Z, A – 2
What fraction of a radioactive material will get disintegrated in a period of two half-lives
  • Whole
  • Half
  • One-fourth
  • Three-fourth
234U has 92 protons and 234 nucleons total in its nucleus. It decays by emitting an alpha particle. After the decay it becomes
  • 232U
  • 232Pa
  • 230Th
  • 230Ra
During negative β–decay
  • Neutron converts into proton
  • Proton converts into neutron
  • Neutron proton ratio increases
  • None of the above
A radioactive nucleus emits a beta particle. The parent and daughter nuclei are
  • Isotopes
  • Isotones
  • Isomers
  • Isobars
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