Question

Why does only 50% insolation reach on earth's surface?

Answer 1

This is called insolation. Only 51% of thisinsolation reaches and is absorbed by the earth's surface. The rest is absorbed by water vapour, dust and clouds, or isreflected by the earth's surface and scattered by particles in the air (the albedo effect).

Answer 2

because many a are between obsarted by cloud s and other things.
(The radiation received on earths surface is insolation).