\(\Delta L = {L_2} - {L_1} = \frac{{{n_2}h}}{{2\pi }} - \frac{{{n_1}h}}{{2\pi }}\)\( \Rightarrow \Delta L = \frac{h}{{2\pi }}({n_2} - {n_1})\)
\( = \frac{{6.6 \times {{10}^{ - 34}}}}{{2 \times 3.14}}(5 - 4)\)\( = 1.05 \times {10^{ - 34}}J{\rm{ - }}S\)