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Nuclei

JEE Main 2026 (Online) 23rd January Evening ShiftMCQEasy📈 Topic in 2% papers+4−1
Ques. 1JEE Main 2026, 23 January (Evening Shift)

Which of the following pair of nuclei are isobars of the element?

  1. 31H and 32He
  2. 19880Hg and 19779Au
  3. 21H and 31H
  4. 23692U and 23892U

Answer

(1) 31H and 32He

Solution

Isobars have the same mass number A but different atomic numbers Z.

(1) 31H, 32He: A = 3 for both, Z different isobars

(2) A = 198 and 197 not isobars (they have the same number of neutrons, 118: isotones)

(3) and (4): same Z, different A isotopes

Answer: (1)

Keep practising — Nuclei

Ques. 2JEE Main 2026, 23 January (Evening Shift)

The average energy released per fission for the nucleus of 23592U is 190 MeV. When all the atoms of 47 g pure 23592U undergo fission process, the energy released is 1023 MeV. The value of is . (Avogadro Number = 6 1023 per mole)

Ques. 3JEE Main 2026, 22 January (Morning Shift)

The minimum frequency of photon required to break a particle of mass 15.348 amu into 4 particles is kHz. [mass of He nucleus = 4.002 amu, 1 amu = 1.66 10-27 kg, h = 6.6 10-34 J s and c = 3 108 m/s]

  1. 14.94 1020
  2. 9 1019
  3. 9 1020
  4. 14.94 1019
Ques. 4JEE Main 2025, 8 April (Evening Shift)

For a nucleus of mass number A and radius R, the mass density of nucleus can be represented as

  1. A 23
  2. Independent of A
  3. A3
  4. A 13
Ques. 5JEE Main 2025, 7 April (Evening Shift)

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below :

  1. (A) is correct but (R) is not correct
  2. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
  3. (A) is not correct but (R) is correct
  4. Both (A) and (R) are correct and (R) is the correct explanation of (A)
Ques. 6JEE Main 2025, 4 April (Evening Shift)

A radioactive material P first decays into Q and then Q decays to non-radioactive material R. Which of the following figure represents time dependent mass of P, Q and R ?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 7JEE Main 2025, 3 April (Morning Shift)

Match the LIST-I with LIST-II Choose the correct answer from the options given below:

  1. A-II, B-I, C-III, D-IV
  2. A-III, B-I, C-II, D-IV
  3. A-III, B-I, C-IV, D-II
  4. A-II, B-I, C-IV, D-III
Ques. 8JEE Main 2025, 2 April (Evening Shift)

Energy released when two deuterons (1H2 ) fuse to form a helium nucleus (2He4 ) is : (Given : Binding energy per nucleon of 1H2 = 1.1 MeV and binding energy per nucleon of 2He4 = 7.0 MeV)

  1. 26.8 MeV
  2. 8.1 MeV
  3. 23.6 MeV
  4. 5.9 MeV
Ques. 9JEE Main 2025, 28 January (Morning Shift)

Choose the correct nuclear process from the below options [p : proton, n : neutron, e- : electron, e+ : positron, : neutrino, : antineutrino]

  1. n p + e+ +
  2. n p + e- +
  3. n p + e+ +
  4. n p + e- +
Ques. 10JEE Main 2025, 23 January (Morning Shift)

A radioactive nucleus n2 has 3 times the decay constant as compared to the decay constant of another radioactive nucleus n1. If initial number of both nuclei are the same, what is the ratio of number of nuclei of n2 to the number of nuclei of n1, after one half-life of n1 ?

  1. 1/4
  2. 1/8
  3. 4
  4. 8
Ques. 11JEE Main 2025, 23 January (Evening Shift)

Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the correct answer from the options given below :

  1. (A) is true but (R) is false
  2. Both (A) and (R) are true and (R) is the correct explanation of (A)
  3. (A) is false but (R) is true
  4. Both (A) and (R) are true but (R) is NOT the correct explanation of (A)

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