Why all points on a wavefront producing secondary wavelets interfere and produce a pattern ONLY when they diffract (via single slit or something) .. Why don't those secondary wavelets interfere just like that always? cause Huygen says, that principle is always true.. so everything should produce interference pattern :P

Question

anonymous · Answer

sorry wrong group :D

fwizbang · Answer

(Not really a math question) They do always interfere in the sense of Huygens. When you have slits or barriers, a lot of the Huygens point sources, so you get patterns, when
you have no barriers, there are no missing sources, and no pattern emerges other than 
normal wave propagation.

anonymous · Answer

i thought that too... but i can't picture it.. ll post it in physics!!