\(P = 25 \times 25;\) \(W = 625\,W\)
\(\frac{\mathrm{hc}}{\lambda} \frac{\mathrm{dn}}{\mathrm{dt}}=\mathrm{P}\)
\(F=\frac{h}{\lambda} \frac{d n}{d t}=\frac{P}{C}=\frac{625}{3 \times 10^{8}}\)
Momentum \(=\frac{625 \times 40 \times 60}{3 \times 10^{8}}=5 \times 10^{-3} \mathrm{Ns}\)
($(h) = 6.63 \times 10^{-34}\, Js$,$e = 1.6 \times 10^{-19}\, C$)