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13.4 Double slit interference
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From one source and two gaps
1st bright fringe
1st bright fringe
central fringe
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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.
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Path difference
Phase difference
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Path difference
Phase difference
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W
First bright fringe
Central fringe
screen
Double Slit interference - theory
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W
First bright fringe
Central fringe
screen
Double Slit interference - theory
Ə
D
= wavelength = 600nmD = slit to screen distance = 2mS = slit separation = 0.5 mmW = fringe width = 1mm
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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
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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
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soh cah toa
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soh cah toa
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soh cah toa
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soh cah toa
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