CHAPTER 11. 2D AND3D WAVEFRONTS 11.5
If you employ Huygens’principle you can see the effect is that the wavefronts are no
longer straight lines.
Each point of the slit acts like a point source. Ifwe think about the twopoint sources
on the edges of the slit and call them A and B then we can go back to the diagram we
had earlier but with some parts blocked by the wall.
�A B� �
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��������If this diagram were showing sound waves thenthe sound would be louder (construc-
tive interference) in some places and quieter (destructive interference) inothers. You
can start to see that there will be a pattern (interference pattern) to the louder and qui-
eter places. If we werestudying light waves then the light would be brighter in some
places than others depending on the interference.
The intensity (how bright or loud) of the interference pattern for a single narrow slit
looks like this: