If [Cu(H₂O)₄]²⁺ absorbs a light of wavelength 600 nm for d-d transition, then the value of octahedral crystal field splitting energy for [Cu(H₂O)₆]²⁺ will be ____________ $\times$ 10^$-$21 J. [Nearest Integer]

(Given : h = 6.63 $\times$ 10^$-$34 Js and c = 3.08 $\times$ 10⁸ ms^$-$1)

$\left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\right]^{2+}$ is tetrahedral <br/><br/> $\left[\mathrm{Cu}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}$ is octahedral <br/><br/> $\because \Delta_{\mathrm{t}}=\frac{4}{9} \times \Delta_{0}$ <br/><br/> $$ \begin{aligned} &\Delta_{\mathrm{t}}=\frac{6.63 \times 10^{-34} \times 3.08 \times 10^{8}}{600 \times 10^{-9}} \\\\ &\Delta_{0}=\frac{9}{4} \times \frac{6.63 \times 10^{-34} \times 3.08 \times 10^{8}}{600 \times 10^{-9}} \approx 765.7 \times 10^{-21} \mathrm{~J} \end{aligned} $$