How many joules of solar energy fall on your back as you work on your tan for 0.70h?

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?

Best answer:

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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