An electron in the hydrogen atom jumps from excited state

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An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, the value of n is

1. 3
2. 4
3. 5
4. 2

Correct Option: B

KE_max = 10eV
φ = 2.75 eV
Total incident energy
E = φ + KE_max = 12.75 eV
∴ Energy is released when electron jumps from the excited state n to the ground state.
E₄ – E₄ = {– 0.85 – (–13.6) ev} = 12.75 eV
∴ value of n = 4