Question
Fri February 10, 2012 By: Renu Suresh

Change of flux of SUNLIGHT?

Expert Reply
Fri February 10, 2012
Solar flux, refers to the rate at which energy is delivered (in watts) per square meter cross section perpendicular to the source (the Sun). So the units are Watts/m2. 
 

Strength of the sunlight might vary depending on the distance of the Earth from the Sun. This turns out to be a very small effect. Althought orbits of planets are elliptical, the orbit of the Earth around the Sun is very close to circular.

Flux involves the normal component coming through an area, so the flux should be greater in the summer when the sunlight is coming in at a more normal angle. It will be less in the winter when the normal component of the sunlight is smaller.
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