Light of wavelength $4000\: A^{\circ}$ and intensity $100 W/m^2$ is incident on a plate of threshold frequency $ 5.5 \times 10^{14}Hz$. The no. of photons incident per $m^2$ per second is

Question

$\begin {array} {1 1} (a)\;2.02 \times 10^{20} & \quad (b)\;2.02 \times 10^{22} \\ (c)\;202 \times 10^{20} & \quad (d)\;202 \times 10^{22} \end {array}$