Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is :

Question

( A ) $9\times10^{15} $
( B ) $3\times10^{19} $
( C ) $9\times10^{17} $
( D ) $3\times10^{16} $