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MHT CET 202625 AprilEvening Shift
Exam
MHT CET
Year
2026
Date
25 April
Shift
Evening Shift
Subject
Physics
Chapter
Atomic Physics

MHT CET 2026 · 25 April · Evening Shift · Physics · Atomic Physics

A hydrogen atom in its ground state is irradiated by light of...

A hydrogen atom in its ground state is irradiated by light of wavelength 1026 A˚1026\ \text{Å}. The electron gets excited to higher energy state nn. Given the ground state energy is −13.6 eV-13.6\ \text{eV} and hc=1242 eV⋅nmhc = 1242\ \text{eV}\cdot\text{nm}, then the value of principal quantum number nn is

Options

  1. A55
  2. B33
  3. C44
  4. D22

Correct answer

B. 33

Step-by-step solution

The energy of the incident photon is given by E=hcλE = \dfrac{hc}{\lambda}

Substituting the given values with λ=102.6\lambda = 102.6 nm:

E=1242102.6≈12.1E = \dfrac{1242}{102.6} \approx 12.1 eV

The energy of the electron in the excited state nn is:

En=E1+EE_n = E_1 + E

En=−13.6+12.1=−1.5E_n = -13.6 + 12.1 = -1.5 eV

The energy of the nn-th state of a hydrogen atom is given by:

En=−13.6n2E_n = \dfrac{-13.6}{n^2} eV

−13.6n2=−1.5\dfrac{-13.6}{n^2} = -1.5

n2=13.61.5≈9n^2 = \dfrac{13.6}{1.5} \approx 9

n=3n = 3

Answer: 3
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