Answer
Frequency (ν) = $4.68\times10^{14}$ Hz
Energy (E) = $3.10\times10^{-19}J$
Work Step by Step
ν = c/λ
c = $2.997925\times10^{8}ms^{-1}$
λ = 641 nm = $641\times10^{-9}m$
ν = $\frac{2.997925\times10^{8}ms^{-1}}{641\times10^{-9}m}$ = $4.68\times10^{14}s^{-1}$
E = hν
h = $6.626\times10^{-34}Js$
ν = $4.68\times10^{14}s^{-1}$
E = $6.626\times10^{-34}Js\times4.68\times10^{14}s^{-1}$ = $3.10\times10^{-19}J$
