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For the wavelength λ = 975 Å, calculate the number of spectral lines emitted when an electron transitions from n = 4 to n = 1.

1. n(n − 1)/2
2. n(n + 1)/2
3. n(n − 1)
4. n(n + 1)

Correct answer: n(n − 1)/2

Solution

The number of spectral lines emitted during a transition from a higher energy level (n = 4) to a lower energy level (n = 1) is given by the formula n(n − 1)/2, where n is the initial energy level. Substituting n = 4, the number of lines is 4(4 − 1)/2 = 6.

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