Question

If ‘I’ is the intensity of the solar radiation at a distance ‘x’ from the surface of the Sun, and if ‘A’ is the surface area of a solar flat plate collector placed at x, with its surface directly facing the sun, and with ‘I’ and ‘A’ given in SI units, the power falling on the collector is given by _________ Watts

Answer 1

surface area of solar flat plate = A
Let radius of solar flat plate is r
then, 4πr² = A
r = $\sqrt{\frac{A}{4\pi}}$

now, separation between source to observation point, R = radius of solar flat + x
= $\sqrt{\frac{A}{4\pi}}$ + x

so, surface area of spherical surface of radius R , A' = 4πR²
$A'=4\pi\{\sqrt{\frac{A}{4\pi}}+x\}^2$

now, intensity = power/area
so, power = intensity × area
= $I.4\pi\{\sqrt{\frac{A}{4\pi}}+x\}^2$