Question

At the given point of time, the earth receives energy from the sun at 4 cal cm^–2 min^–1. Determine the number of photons received on the surface of the Earth per cm2 per minute. (Given: Mean wavelength of sunlight = 5500 Å)

Answer 1

E = 4 calorie = 4 × 4.184 J

λ = 5500 Å

Number of photons received on the surface of the earth, from E = nhv

n = `("E"λ)/"hc"`

= `(4 xx 4.184 xx 5500 xx 10^-10)/(6.6 xx 10^-34 xx 3 xx 10^8)`

= `(9.2048 xx 10^-10)/(19.8 xx 10^-26)`

= 4648 × 10¹⁶

= 4.648 × 10¹⁹

n = 4.65 × 10¹⁹