$Ti ^{+3}: 3 d ^1$

$C.F.S.E.$ $=-0.4 \times \Delta_0$

$=-\frac{96 \times 10^3}{ N _0}\,J$

$\Delta_0=\frac{96 \times 10^3}{0.4 \times 6 \times 10^{23}}$

$\frac{ hc }{\lambda}=\frac{96 \times 10^3}{0.4 \times 6 \times 10^{23}}$

$\lambda=\frac{0.4 \times 6 \times 10^{23} \times 6.4 \times 10^{-34} \times 3 \times 10^8}{96 \times 10^3}$

$=0.48 \times 10^{-6}\,m$

$=480 \times 10^{-9}\,m$

$=480\,nm$