# A 200 W sodium street lamp emits yellow light of wavelength $0.6 \mu m$. Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is .
( A ) $3 \times10^{19}$
( B ) $62 \times10^{20}$
( C ) $6 \times 10^{18}$
( D ) $1.5\times 10^{20}$