## Chemistry: Principles and Practice (3rd Edition)

$3.1\times10^{-19}J$
E=hν = hc/λ h = $6.626\times10^{-34}Js$ c = $2.997925\times10^{8}ms^{-1}$ λ = 640 nm = $640\times10^{-9}m$ E = $\frac{6.626\times10^{-34}Js\times2.997925\times10^{8}ms^{-1}}{640\times10^{-9}m}$ = $3.1\times10^{-19}J$