What is Diffraction.and why?

                     

Diffraction
Definition. The flaring out or enrouchment
Of the light in the region on geometrical  shadow.
When light passes through sharp edges or obstacles.
 
Or
The phenomenon of bending of light from any sharp edges or obstacles.

Condition for diffraction

Size of aperture or obstacles nearly same to wavelength of light. Then diffraction pattern observed.

 Here AA' and BB'are shadow region where light comes after diffraction.

Here AB is the shadis region where light comes after diffraction through sharp edges.



How diffraction occur
Due to superposition of secondary wavelets diffraction phenomenon occur.


Types of deffraction
There are two types of defraction
1 Fresnel diffraction
2Fraunhoffer diffraction

Difference between Fresnel or Fraunhofer diffraction

✓In Fresnel diffraction distance between source and screen is finite.
✓There is no use of any lenses .



$In Frauhoffer diffraction distance between source and screen is infinite.
$In which we use lense.

General examples of diffraction
Listening of one room sound in another room .
This is sound diffraction.

Light of one room reached in another room by windows and doors.
This is light diffraction.

Here we can't see diffraction pattern by our eyes because these obstacles are very larges In size.