Two nuclei have mass numbers in the ratio 1:27. The ratio of their nucleus radii will be, respectively:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( \displaystyle\frac{1}{3} \)
The radius of a nucleus depends on its mass number A as \( R = R_0A^{1/3} \), where \( R_0 \) is a constant (about 1.2 fm), so \( R \propto A^{1/3} \).
\( \displaystyle \frac{R_1}{R_2} = \left(\frac{A_1}{A_2}\right)^{1/3} \)
\( \displaystyle \frac{R_1}{R_2} = \left(\frac{1}{27}\right)^{1/3} = \frac{1}{3} \)
Note: NTA picked this question from an NCERT (2026-27) exercise and changed the figures. Do not ignore NCERT while practising numericals.
NCERT (2026-27):
Exercises – …
