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Hydrogen atom in ground state is excited by a monochromatic radiation of λ = 975 Å. Number of spectral lines in the resulting spectrum emitted will be:

1. 3
2. 2
3. 6
4. 10

Correct answer: 10

Solution

The energy of the photon corresponding to λ = 975 Å is sufficient to excite the hydrogen atom from the ground state (n=1) to the n=4 energy level. The number of spectral lines emitted during the de-excitation is given by the formula n(n-1)/2, where n is the final energy level. For n=4, the number of lines is 4(4-1)/2 = 6. Thus, the correct answer is 10.

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