Step 1: Understanding the Concept:
Orbital angular momentum is quantised in quantum mechanics. It depends on azimuthal quantum number \(l\).
Step 2: Detailed Explanation:
Quantum mechanical expression: \(L = \sqrt{l(l+1)}\,\hbar\), where \(\hbar = \frac{h}{2\pi}\), \(l = 0,1,2,..........,(n-1)\). This replaces Bohr’s expression: \(L = n\hbar\).
Step 3: Final Answer:
\[
\boxed{L = \sqrt{l(l+1)}\,\frac{h}{2\pi}}
\]