Question & Answer: How many photons are produced in a laser pulse of 0.896 J at 489 nm?…..

E = hv

C = v

v    = C/

E   = hC/

   = 489nm = 489*10^-10 m

E   = 6.625*10^-34 * 3*10^8/489*10^-10

= 4.064*10^-18 J

no of photons    = 0.896j* photon/4.064*10^-18J    = 1.93*10^17 photons