Question

The power of light emitted by the sun is 3.9× 10²⁶ W.Assuming the mean wavelength of sunlight to be 6000 Å, calculate the photon flux arriving at 1 m² area on earth perpendicular to light radiations. The average radius of earth’s orbit around sun is 1.49 × 10¹¹ m.

Answer 1

Power of light emitted by the sun, W = 3.9 × 10²⁶ W

r = earth sun mean distance = 1.49 × 10¹¹ m

λ = mean wavelength of sun light = 6000 Å = 6 × 10^–7 m

Intensity of light an earth,

Power received by area A on earth, W ' = I ×A

but, W ' = n' hν, where n' is the number of photon incident per sec or photon-flux