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What can be the change in orbital angular momentum when an electron undergoes a transition inside a hydrogen atom?

1. h / (4*pi)
2. h / pi
3. h / (2*pi)
4. h / (8*pi)

Correct answer: h / (2*pi)

Solution

In the Bohr model, orbital angular momentum L = n * h/(2*pi) where n = 1,2,3,... For a transition from n1 to n2: delta_L = (n2 - n1) * h/(2*pi). The minimum change (for |n2-n1|=1) is h/(2*pi) = hbar. This is also consistent with quantum mechanics where changes in l (orbital quantum number) must satisfy deltaₗ = +-1, giving delta_L changes of order hbar. The allowed change is an integer multiple of h/(2*pi).

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