During Sunset why is part of the sky still blue, sunlight now traverse further why isnt the whole sky reddish?

Question

In many photos sunset are only orange around the sun which sits in the middle of the photos, the part of the sky nearer to us is blue or purple.

Since the sunlight now travels further to reach us why is the part of the sky which is further from the sun but nearer to us blue.. shouldn't it be orange?

e.g. is this photo

http://www.agt.net/public/dhauschi/images/Jamaica_sunset.jpg

Answer 1

The earth's atmosphere acts as a prism.  Longer wavelengths (Red) bend less than shorter wavelengths (blue), so appear closer to the source (the sun).