COMEDK 2026 Afternoon Shift | Atoms and Nuclei Question 1 | Physics

A hydrogen atom absorbs energy and rises to $n=3$ state from its ground state $n=1$. If the potential energy of the atom at its ground state is -13.6 eV , find the wave length emitted by it when it returns to its ground state:

{Planck's constant $=6.6 \times 10^{34} \mathrm{~J} \mathrm{~s}$ }

$12000^{\circ} \mathrm{A}$

$1020^{\circ} \mathrm{A}$

$7000^{\circ} \mathrm{A}$

$4000^{\circ} \mathrm{A}$

COMEDK 2026 Afternoon Shift

MCQ (Single Correct Answer)

-0

The main function of cadmium used in the nuclear reactor is:

It removes the heat produced at the core of the reactor

It gives energy to the secondary neutrons produced in the nuclear fission

It slows down the fast moving secondary neutrons produced during the nuclear fission

To capture the slow neutron produced in the nuclear reactor

COMEDK 2026 Afternoon Shift

MCQ (Single Correct Answer)

-0

What is the frequency of the electron in the first orbit of hydrogen atom of orbital radius $0.5 \times 10^{-10} \mathrm{~m}$, if its orbital velocity in that orbit is $2.2 \times 10^6 \mathrm{~ms}^{-1}$.

$3.49 \times 10^{15} \mathrm{~Hz}$

$3.49 \times 10^{13} \mathrm{~Hz}$

$6.98 \times 10^{15} \mathrm{~Hz}$

$6.98 \times 10^{13} \mathrm{~Hz}$

COMEDK 2026 Afternoon Shift

MCQ (Single Correct Answer)

-0

If the ratio of the nuclear radii of two atoms is $2: 3$ then the ratio of their mass numbers is:

$8: 27$

$4:9$

$ 27:8$

$9: 4$

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