Radiation pressure for \(0 \%\) reflection \(=\frac{I}{\mathrm{C}}\)
Hence, in given case, radiation pressure \( = (0.25)\left( {\frac{{2I}}{{\text{C}}}} \right) + (0.75)\left( {\frac{I}{{\text{C}}}} \right)\)
\( = (1.25)\left( {\frac{I}{{\text{C}}}} \right)\)
Force \(=\mathrm{P} \times(\text { Area })\)
\(=20.83 \times 10^{-8}\, \mathrm{N}\)