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13.4 Double slit interference
From one source and two gaps
1st bright fringe
1st bright fringe
central fringe
From one source and two gaps
1st bright fringe
1st bright fringe
central fringe
- the closer the slits become the wider the fringe separation.
- waves of short wavelength give narrow fringe separation because blue light diffracts less.
Path difference
Phase difference
Path difference
Phase difference
W
First bright fringe
Central fringe
screen
Double Slit interference - theory
W
First bright fringe
Central fringe
screen
Double Slit interference - theory
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D
= wavelength = 600nmD = slit to screen distance = 2mS = slit separation = 0.5 mmW = fringe width = 1mm
For constructive interference at the screen:( ie a bright fringe )
Wave fronts from S1 and S2 must arrive at the screen in phase with a path difference of a whole number of wavelengths
For constructive interference at the screen:( ie a bright fringe )
Wave fronts from S1 and S2 must arrive at the screen in phase with a path difference of a whole number of wavelengths
For destructive interference at the screen:( ie a dark fringe )
Wave fronts from S1 and S2 must arrive out of phase with a path difference of half a wavelength
soh cah toa
soh cah toa
soh cah toa
soh cah toa