**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 33 cm x 53 cm rectangle.**

**How many joules of solar energy fall on your back as you work on your tan for 1.4 h?**

Intensity = 1.4 Kw/m2

1.1 hr = 1.1 x 60

= 66 minutes

1400 x .34 x .53 x 66 x 60

Intensity = 1.4 Kw/m 21.1 hr = 1.1 x 60= 66 minutes

1400 x .34 x .53 x 66 x 60

=9.99 x 10^{5}

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