JEE Main 2026 (Online) 21st January Morning Shift | Atoms and Nuclei Question 26 | Physics

If an alpha particle with energy 7.7 MeV is bombarded on a thin gold foil, the closest distance from nucleus it can reach is $\_\_\_\_$ m. (Atomic number of gold $=79$ and $\frac{1}{4 \pi \epsilon_{\mathrm{o}}}=9 \times 10^9$ in SI units)

$2.95 \times 10^{-16}$

$3.85 \times 10^{-14}$

$2.95 \times 10^{-14}$

$3.85 \times 10^{-16}$

JEE Main 2025 (Online) 8th April Evening Shift

MCQ (Single Correct Answer)

-1

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

$A^{\frac{2}{3}}$

Independent of A

$A^3$

$A^{\frac{1}{3}}$

JEE Main 2025 (Online) 7th April Evening Shift

MCQ (Single Correct Answer)

-1

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : The density of the copper $(^ {64}_{29} \text{Cu})$ nucleus is greater than that of the carbon $(^ {12}_{6} \text{C})$ nucleus.

Reason (R) : The nucleus of mass number A has a radius proportional to $ A^{1/3} $.

In the light of the above statements, choose the most appropriate answer from the options given below :

(A) is correct but (R) is not correct

Both (A) and (R) are correct but (R) is not the correct explanation of (A)

(A) is not correct but (R) is correct

Both (A) and (R) are correct and (R) is the correct explanation of (A)

JEE Main 2025 (Online) 7th April Morning Shift

MCQ (Single Correct Answer)

-1

In a hydrogen like ion, the energy difference between the $2^{\text {nd }}$ excitation energy state and ground is 108.8 eV . The atomic number of the ion is: