Question by ginger_jj:
How many joules of solar energy fall on your back as you work on your tan for 0.70h?
The intensity of electromagnetic waves from the sun is 1.4 kW/m^2 just above the earth’s atmosphere. Eighty percent of this reaches the surface at noon on a clear summer day.
Suppose you model your back as a 27cm & 51cm rectangle.
How many joules of solar energy fall on your back as you work on your tan for 0.70h?


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Answer by WhatGoes Around Comes Around
80% of 1.4 = 1.12 kW / m²

Area = 0.27 * 0.51 = 0.138 m²

Power = 1.12 * 0.138 = 0.154 kW

Energy = Power * Time
Time = 0.7 * 3600 = 2520 seconds

Energy = 0.154 * 2520 = 389 Joules

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