Sol. $$ \begin{aligned} & \mathrm{L}=m v r \quad \mathrm{r} \propto \mathrm{n}^2, \quad \mathrm{v} \propto \frac{1}{\mathrm{n}} \\ & \therefore \mathrm{~L} \propto \mathrm{n} \end{aligned} $$ Also, $\mathrm{L}=\frac{\mathrm{nh}}{2 \pi}$, Bohr orbit is, $\mathrm{L}_1=\mathrm{L}=\frac{1 \cdot h}{2 \pi}$ $$ \begin{aligned} & L_2=2[L]=2 L \\ & L_2=\frac{2 h}{2 \pi} \end{aligned} $$ So, change $=\mathrm{L}_2-\mathrm{L}_1=2 \mathrm{~L}-\mathrm{L}=\mathrm{L}$