If  a beam of light is passed through a wide opening, it passes through with little or no diffraction. However, if the opening is small, the wave property of light often produce unusually looking pattern - consisting of bright fringe (called central maximum), the dark fringes  and the less-intense bright fringes (called the secondary maxima)
•HOOK:
Teacher reviews Diffraction of waves with the class by asking probing questions like explanation of how diffraction occurs.


•ACTION:
Teacher discusses single-slit diffraction and
the conditions that should exist for it to occur.
Fraunhofer diffraction is discussed as a special case of diffraction that shows distinctive
differences between the central fringe and darker flanking fringes.



•Consolidation:
Teacher uses appropriate problem to show how to determine the width of the central maximum of
Fraunhofer’s diffraction.


 
 


 
 
  


Picture
Fig: Image of Single-slit  diffraction
Source:
http://en.wikipedia.org/wiki/Diffraction

Picture
   Fig: Diffraction of red laser beam on the hole
Source: http://en.wikipedia.org/wiki/Diffraction