JEE Questions for Physics Atoms And Nuclei Quiz 25 - MCQExams.com


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The composition of an a-particle can be expressed as
  • 1P + 1N
  • 1P + 2N
  • 2P + 1N
  • 2P + 2N
A nucleus of mass 214 amu in free state decays to emit an α–particle. Kinetic energy of the α–particle emitted is 6.7 MeV. The recoil energy (in MeV) of the daughter nucleus is
  • 1.0
  • 0.5
  • 0.25
  • 0.125
The particle that possesses half integral spin as
  • Photon
  • Pion
  • Proton
  • K-meson
In a sample of radioactive material, what fraction of the initial number of active nuclei will remain undisintegrated after half of a half-life of the sample?

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A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to 1% of its original value
  • 3.2T year
  • 4.6T year
  • 6.6T year
  • 9.2T year
Pick out the incorrect statement from the following
  • β–emission from the nucleus is always accompanied with a neutrino
  • The energy of the α–particle emitted from a given nucleus is always constant
  • γ–ray emission makes the nucleus more stable
  • Nuclear force is charge-independent
  • Fusion is the main process by which energy is released from a star
A radioactive nucleus of mass M emits a photon of frequency v and the nucleus recoils. The recoil energy will be

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  • Zero
The half life of a radioactive isotope X is 50 years. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1 : 16 in a sample of a given rock. The age of the rock was estimated to be
  • 100 years
  • 150 years
  • 200 years
  • 250 years
A mixture consists of two radioactive materials A1 and A2 with half lives of 20 s and 10 s respectively. Initially the mixture has 40 g of A1 and 160 g of A2. The amount of the two in the mixture will become equal after
  • 60 s
  • 80 s
  • 20 s
  • 40 s
A sodium atom is in one of the states labeled \'Lowest excited levels\'. It remains in that state for an average time of 10–8 s, before to makes a transition back to a ground state. What is the uncertainty in energy of that excited state
  • 6.56 × 10–8 eV
  • 2 × 10–8 eV
  • 10–8 eV
  • 8 × 10–8 eV
A hydrogen atom in its ground state absorbs 10.2 eV of energy. The orbital angular momentum is increased by
(Given Planck\'s constant h = 6.6 × 10–34 J - s
  • 1.05 × 10–34 J-s
  • 3.16 × 10–34 J-s
  • 2.11 × 10–34 J-s
  • 4.22 × 10–34 J-s
Hydrogen (H), deuterium (D), singly ionized helium (He+) and doubly ionized lithium (Li++) all have one electron around the nucleus. Consider n = 2 to n =1 transition. The wavelengths of emitted radiations are λ1, λ2, λ3 and λ4 respectively. Then approximately
  • λ1 = λ2 = 4λ3 = 9λ4
  • 4λ1 = 2λ2 = 2λ3 = λ4
  • λ1 =2λ2= 2√2λ3 =3√2λ4
  • λ1 = λ2 = 2λ3 = 3√2λ4
Consider an electron (m = 9.1 x 10-31 kg) confined by electrical forces to move between rigid walls separated by 1.0 x 10-9 metre, which is about five atomic diameters. The quantised energy value for the lowest stationary state is
  • 12 x 1010-20 J
  • 6.0 x 10-20 J
  • 6.0 x 10-18 J
  • 6 J
In a hypothetical Bohr hydrogen, the mass of the electron is doubled. The energy E0 and the radius r0 of the first orbit will be (a0 is the Bohr radius)
  • E0 = – 27.2 eV; r0 = a0 /2
  • E0 = – 27.2 eV; r0 = a0
  • E0 = –13.6 eV; r0 = a0 /2
  • E0 = – 13.6 eV; r0 = a0
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 (Ionization energy of hydrogen atom is 13.6 eV
  • 182.51 Å
  • 177.17 Å
  • 142.25 Å
  • 113.74 Å
The ionization 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
An electron passing through a potential difference of 4.9 V collides with a mercury atom and transfers it to the first excited state. What is the wavelength of a photon corresponding to the transition of the mercuryatom to its normal state
  • 2050 Å
  • 2240 Å
  • 2525 Å
  • 2935 Å
The sun radiates energy in all directions. The average radiations received on the earth surface from the sun is 1.4 kilowatt/m2. The average earth sun distance is 1.5 × 1011metres. The mass lost by the sun per day is (1 days = 86400 seconds)
  • 4.4 × 109 kg
  • 7.6 × 1014 kg
  • 3.8 × 1012 kg
  • 3.8 × 1014 kg
The activity of a radioactive sample is measured as N0 counts per minute at t = 0 and N0 /e counts per minute at t = 5 minutes. The time (in minutes) at which the activity reduces to half its value is

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A star initially has 1040 deuterons. It produces energy via the processes 1H2 + 1H2→1H3 + p1H2 + 1H3 →2He4 + n The masses of the nuclei are as follows M(H2) = 2.014 amu; M(p)= 1.007 amu; M(n) =1.008 amu; M(He4) = 4.001 amu
If the average power radiated by the star is 1016 W, the deuteron supply of the star is exhausted in a time of the order of
  • 106 s
  • 108 s
  • 1012 s
  • 1016 s
A nucleus with mass number 220 initially at rest emits anα–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
From a newly formed radioactive substance (Half life 2 hours), the intensity of radiation is 64 times the permissible safe level. The minimum time after which work can be done safely from this source is
  • 6 hours
  • 12 hours
  • 24 hours
  • 128 hours
A radioactive material decays by simultaneous emission of two particles with respective half lives 1620 and 810 years. The time (in years) after which one-fourth of the material remains is
  • 1080
  • 2430
  • 3240
  • 4860
For a substance the average life for α–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 (P0) is 138.6 days. For ten lakh Polonium atoms, the number of disintegrations in 24 hours is
  • 2000
  • 3000
  • 4000
  • 5000
A radioactive nucleus undergoes α–emission to form a stable element. What will be the recoil velocity of the daughter nucleus if v is the velocity of α–emission and A is the atomic mass of radioactive nucleus

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Half-life of a radioactive substance is 20 minutes. Difference between points of time when it is 33% disintegrated and 67% disintegrated is approximately
  • 10 min
  • 20 min
  • 30 min
  • 40 min
Two radioactive materials X1 and X2have decay constants 10λ and λ respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X1 to that of X2will be 1 /e after a time
  • 1 /(10λ)
  • 1 /(11λ )
  • 11 /(10λ)
  • 1 /(9λ )
Half life of a radio-active substance is 20 minutes. The time between 20% and 80% decay will be
  • 20 minutes
  • 40 minutes
  • 30 minutes
  • 25 minutes
Mass spectrometric analysis of potassium and argon atoms in a Moon rock sample shows that the ratio of the number of (stable) 40Ar atoms present 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 × 1011yr
  • 2.95 × 109yr
  • 4.37 × 109yr
  • 4.37 × 1011yr
If one starts with one curie of radioactive substance(T1/2 = 12 hrs) the activity left after a period of 1 week will be about
  • I curie
  • 120 micro curie
  • 60 micro curie
  • 8 mili curie
Two radioactive nuclei P and Q, in a given sample decay into a stable nucleus R. At time t = 0, number of P species are 4 N0 and that of Q are N0. Half-life of P (for conversion to R) is 1 minute where as that of Q is 2 minutes. Initially there are nonuclei of R present in the sample. When number of nuclei of P and Q are equal, the number of nuclei of R present in the sample would be

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An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be
  • 24 hR/25 m
  • 25 hR/24 m
  • 25 m/24 hR
  • 24 m/25 hR
The dependence of binding energy per nucleon, BNonthe mass number, A is represented by

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A radioactive sample has N0 active atoms at t = 0. If the rate of disintegration at any time is R and the number of atoms is N, then the ratio R /N varies with time as

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The count rate of 10 g of radioactive material was measured at different times and this has been shown in the figure. The half life of material and the total counts (approximately) in the first half life period, respectively are
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  • 4h, 9000
  • 3h, 14000
  • 3h, 235
  • 3h, 50
The fraction f of radioactive material that has decayed in time t, varies with time t. The correct variation is given by the curve
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  • A
  • B
  • C
  • D
In figure X represents time and Y represents activity of a radioactive sample. Then the activity of sample, varies with time according to the curve
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  • A
  • B
  • C
  • D
The graph which represents the correct variation of logarithm of activity (log A) versus time, in figure is
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  • A
  • B
  • C
  • D
The charge density in a nucleus varies with distance from the centre of the nucleus according to the curve in figure

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The graph between number of decayed atoms N\' of a radioactive element and time t is

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  • 4
  • 3
  • 2
  • 1
The energy spectrum of β–particles [number N (E) as a function of β–energy E] emitted from a radioactive source is

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Assertion It is not possible to use 35Cl as the fuel for fusion energy
Reason The binding energy of 35Cl is too small
  • If both Assertion and reason are true and the Reason is the correct explanation of the assertion.
  • If both Assertion and Reason are true but reason is not the correct explanation of the assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion 90Sr from the radioactive falling out from a nuclear bomb ends up in the bones of human beings through the milk consumed by them. It causes impairment of the production of red blood cells
Reason The energetic β–particles emitted in the decay of 90Sr damage the bone marrow
  • If both Assertion and reason are true and the Reason is the correct explanation of the assertion.
  • If both Assertion and Reason are true but reason is not the correct explanation of the assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
Assertion Neutrons penetrate matter more readily as compared to protons
Reason Neutrons are slightly more massive than protons
  • If both Assertion and reason are true and the Reason is the correct explanation of the assertion.
  • If both Assertion and Reason are true but reason is not the correct explanation of the assertion.
  • If Assertion is true but Reason is false.
  • If the Assertion and Reason both are false.
  • If Assertion is false but Reason is true.
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