At noon on a clear day, sunlight reaches the earth\'s surface at madison, wisconsin, with an average intensity of approximately 2.00 kj·s–1·m–2. if the sunlight consists of photons with an average wavelength of 510.0 nm, how many photons strike a 4.80 cm2 area per second?

I = average intensity of sunlight reaching at Madison = 2000 Js⁻¹m⁻²

A = area on which the light strike = 4.80 cm² = 4.80 x 10⁻⁴ m²

energy received per second by the area is given as

E = IA

inserting the values

E = (2000) (4.80 x 10⁻⁴)

E = 0.96 J

λ = wavelength of the photons in the sunlight = 510 x 10⁻⁹ m

c = speed of light = 3 x 10⁸ m/s

h = plank's constant = 6.63 x 10⁻³⁴ J-s

n = number of photons received per second

energy received per second is also given as

E = n h c /λ

inserting the values

0.96 = n (6.63 x 10⁻³⁴) (3 x 10⁸) /(510 x 10⁻⁹)

n = 2.5 x 10¹⁸ per second

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.