Question

Assertion (A): The isotope \[ {}^{235}_{\phantom{1}92}\mathrm{U} \] is more easily fissionable than the isotope \[ {}^{238}_{\phantom{1}92}\mathrm{U} \].

Reason (R): The fission of \[ {}^{238}_{\phantom{1}92}\mathrm{U} \] nucleus is possible even by slow neutrons, while the fission of the \[ {}^{235}_{\phantom{1}92}\mathrm{U} \] nucleus can occur only by fast neutrons.

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

• Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).

• Assertion (A) is false, but Reason (R) is true.

• Assertion (A) is true, but Reason (R) is false.

Answer 1

Assertion (A) is true, but Reason (R) is false.

Explanation:

Uranium-235 is easily fissionable by slow (thermal) neutrons, while uranium-238 requires fast neutrons and is less easily fissionable. Therefore, Assertion (A) is true. Reason (R) states the opposite, so it is false.