Question

all about interference of light

Answer 1

Interference is the interaction between waves traveling in the same medium. When two waves come into contact, depending on the phase differences along the waves, constructive and destructive interferences will occur.
From: http://library.thinkquest.org/27356/p_interference.htm

Here's an animation thingo that you can play with interference in http://vsg.quasihome.com/interfer.htm

Answer 2

Aaand this is a tutorial on it http://www.matter.org.uk/schools/content/Interference/introduction.html (hit 'next' up the top for more)