Condition for generating a stable interference pattern
Coherent waves are two circular waves of same frequency, wavelength, amplitude and phase
Coherent sourcesCoherent sources are the wave sources
that produce coherent waves
Constructive interference I
When a crest meets a crest, the two waves reinforce each other
Constructive interference II
When a trough meets a trough, the two waves reinforce each other
Destructive interference
When a crest meets a trough, the two waves cancel each other
X
Path difference
Path difference at X
= |S1X - S2X|
Constructive interference
Point Path differenceP 0Q R 2V
Path difference = n,
n = 0, 1, 2, …
Destructive interference
Point Path differenceU /2W 3/2
...0,1,2,....2
1difference Path
nn ,
Antinodal lines (A)
Antinodal lines :lines that link up the points of constructive interference of the same path difference
Nodal lines (N)
Nodal lines :
lines that link up the points of destructive interference of the same path difference
Increase the density of nodal and antinodal lines
increase the separation of two sources
Increase the density of nodal and antinodal lines
decrease the wavelength
Interference and energy redistribution
•According to the law of conservation of energy, energy cannot be created nor destroyed
• Interference is just a process of energy redistribution
energy at the points of destructive interference
energy at the points of constructive interference
The End
Video on ripple tank experiment