A 50 watt bulb emits monochromatic red light of wavelength of 795 nm . The number of photons emitted per second by the bulb is $x \times 10^{20}$. The value of $x$ is $\_\_\_\_$ . [Given : $\mathrm{h}=6.63 \times 10^{-34} \mathrm{Js}$ and $\mathrm{c}=3.0 \times 10^8 \mathrm{~ms}^{-1}$ ]