$A$ beam of light with intensity $10^{-3} \text{ W m}^{-2}$ and cross-sectional area $20 \text{ cm}^2$ is incident on a fully reflective surface at an angle of $45^{\circ}$. The force exerted by the beam on the surface is:

  • A
    $2.3 \times 10^{-15} \text{ N}$
  • B
    $1.33 \times 10^{-14} \text{ N}$
  • C
    $6.67 \times 10^{-15} \text{ N}$
  • D
    $9.4 \times 10^{-15} \text{ N}$

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