MCQEasyJEE 2023Bohr's Model & Hydrogen Spectrum

JEE Physics 2023 Question with Solution

The energy levels of a hydrogen atom are shown. The transition corresponding to emission of the shortest wavelength is:

  • A

    A

  • B

    D

  • C

    C

  • D

    B

Answer

Correct answer:B

Step-by-step solution

Standard Method

Given: The question asks which transition gives emission of the shortest wavelength.

Find: The transition with the maximum energy gap.

For an emitted photon,

ΔE=hcλ\Delta E = \frac{hc}{\lambda}

So,

λ1ΔE\lambda \propto \frac{1}{\Delta E}

For the shortest wavelength, the energy gap must be maximum.

From the given transitions, the correct choice is the transition from n=3n = 3 to n=1n = 1.

Therefore, the correct option is B.

Energy-Wavelength Relation

Given: The energy of a photon emitted during a transition is related to its wavelength.

Find: Which transition corresponds to the shortest wavelength.

The emitted photon satisfies

E=hcλE = \frac{hc}{\lambda}

where hh is Planck's constant, cc is the speed of light, and λ\lambda is the wavelength.

For the shortest wavelength, the emitted energy must be maximum.

Also, for a transition,

E=EinitialEfinalE = E_{\text{initial}} - E_{\text{final}}

So the transition with the largest energy difference gives the shortest wavelength.

The hydrogen atom energy levels are given by

En=13.6eVn2E_n = -\frac{13.6 \, \text{eV}}{n^2}

The solution text indicates that the largest energy difference corresponds to the transition from n=3n = 3 to n=1n = 1.

Therefore, the transition corresponding to the shortest wavelength is D, which is Option 2, so the correct option label is B.

Common mistakes

  • Students may look for the smallest transition length on the diagram instead of the largest energy gap. Wavelength depends on the emitted photon energy, so compare ΔE\Delta E, not visual arrow length.

  • Students may use λΔE\lambda \propto \Delta E, which is incorrect. From ΔE=hcλ\Delta E = \frac{hc}{\lambda}, the wavelength is inversely proportional to the energy gap.

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