Light from the sun has an intensity of about 1400 Wm2 above

Light from the sun has an intensity of about 1,400 W/m2 above the earth’s atmosphere, and 4/5 of that reaches us down on the surface of the earth. Consider your back to be a rectangle measuring 0.5 m by 0.3 m. How much solar energy, in joules, is transferred to your back if you lie on your stomach for one hour?

Solution

The Intensity which reaches surface of the earth is

I=(4/5)*1400 =1120 W/m²

Since Intensity

I=P/A

=>P=IA =1120*(0.5*0.3)

P=168 W

Solar Energy delivered in on hour

E=Pt =168*(1*60*60)

E=6.048*10⁵ J