the coherence length \(L=c \tau_0=(3*10^8 m/s)(10^{-6}s)=300m\)

The bandwidth is \(\Delta \nu=\frac{1}{\tau_0}=\frac{1}{10^{-6}s}=10^6 Hz\)

\(\Delta \lambda=\frac{\lambda^2}{L}=\frac{(632.8nm)^2}{300m}=1.33*10^{-15}m\)