### Two source interference constructive interference ------destructive interference ------- Two source interference Path difference = S2P – S1P = 1 wavelength = P constructive interference ------destructive interference.

```Two source interference
constructive interference ------destructive interference -------
Two source interference
Path difference = S2P – S1P
= 1 wavelength
=
P
constructive interference ------destructive interference -------
S1
S2
Two source interference
Path difference for constructive interference = n 
(where n is an integer)

0
2
3
constructive interference ------destructive interference -------
Two source interference
Path difference for destructive interference =
(n + ½) 
(where n is an integer)
½
1½ 
2½ 
constructive interference ------destructive interference -------
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Two source interference
The path difference is
• n for constructive interference
• (n + ½)  for destructive interference
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