Question

Suppose a person lying flat on the beach and the rate of absorption of energy from the sun is 500 W. Find the angle of incidence of the sun's rays along the horizontal. (The surface area of ​​the body is 0.8 m², emission = 0.7).​

Answer 1

Given:

• Rate of absorption of energy from the sun = 500 W
• Surface area of the body = 0.8 m²
• Emission = 0.7

To find:

• Angle of incidence of the sun's rays along the horizontal.

Answer:

• $\frac{dQ}{dt} = IeAcos \alpha$  = 500 W

        where, α = angle of incidence of the sun rays with the horizontal

                     e = emmisivity

                     A = area

                      I = solar energy density = 1000 W/m²

•   500 = 1000 *0.7 *0.8 cos α  

      ⇒ α = 26.77 °

• Angle of incidence of the sun's rays along the horizontal = 26.77 °