Answer:
3.2 x 10^18
Explanation:
Power, P = 1 W = 1 J/s
wavelength, λ = 620 nm = 620 x 10^-9 m
Energy of each photon, E = hc/λ
where, h is the Plank's constant and c be the velocity of light
E = (6.63 x 10^-34 x 3 x 10^8) / (620 x 10^-9)
E = 3.2 x 10^-19 J
Let n be the number of photons per second
n = Total energy in one second / energy of each photon
n = 1 / (3.2 x 10^-19)
n = 3.2 x 10^18 photons per second
So, the rate of photons is 3.2 x 10^18.
