(a) Two sources generate light at wavelengths of $\lambda=480 \mathrm{~nm}$ and $\lambda=725 \mathrm{~nm}$, respectively. What are the corresponding photon energies? ( $b$ ) Three sources generate light with photon energies of $E=0.87 \mathrm{eV}, E=1.32 \mathrm{eV}$, and $E=1.90 \mathrm{eV}$, respectively. What are the corresponding wavelengths?