When an electron in hydrogen atom is excited, from its 4th to 5th stationary orbit, the change in angular momentum of electron is (Planck’s constant: $\mathrm{h}=6.6\times {10}^{-34}\mathrm{J}\text{ - s}$) 

Change in Angular Momentum

The change in angular momentum is given as:

ΔL = L₂ - L₁ = (n₂h / 2π) - (n₁h / 2π)

Simplifying:

ΔL = (h / 2π)(n₂ - n₁)

Substitute the values:

ΔL = (6.6 × 10^-34) / (2 × 3.14) × (5 - 4)

Final calculation:

ΔL = 1.05 × 10^-34 J·s