At noon on a clear day, sunlight reaches the earth's surface at Madison, Wisconsin, with an average intensity of approximately 5.00 5.00 kJ·s−1·m−2. If the sunlight consists of photons with an average wavelength of 510.0 nm, how many photons strike a 7.00 7.00 cm2 area per second?

7.175*10^18

Explanation:

Energy of a wave:

E = nhc/λ, where

E = energy of the wave

n = no of photons

h = Planck's Constant

c = speed of light

λ = wavelength of the wave

4000 = (n * 6.63*10^-34 * 3*10^8) / (510*10^-9)

4000 = 1.989*10^-25 * n / 510*10^-9

4000 = 3.9*10^-19 * n

n = 1.025*10^22 photons per second per meter²

7.0 cm² = 7.0 / 10,000 m²

= 7 x 10⁻⁴

Photons per second = 1.025*10^22 * 7 x 10⁻⁴

= 7.175*10^18 photons per second