What is path length difference?

[seang]

My text keeps referring to it but I have no idea what it refers to.

 

[berkeman]

Depends on the context. But in the context of integrals, you can often have your integration follow different paths for the convenience of the math.

 

[Hootenanny]

In physics when studying interference patterns it is simply the difference in distance traveled between two waves or secondary wavelets/

~H