The basic difference between Fresnel and Fraunhofer diffraction is that in Fresnel diffraction the source of light and screen is at a finite distance from the obstacle, while in Fraunhofer diffraction if the source of light and screen is at an infinite distance from the obstacle.
what is Fresnel’s diffraction?
Fresnel diffraction can be observed if the source of light and the screen at which the diffraction pattern is formed are kept at a finite distance from the diffracting obstacle. In this situation, the wavefronts falling on the obstacle are not planes. Similarly, the wavefronts leaving the obstacle are not plane.
Read also: Diffraction of light
what is Fraunhofer diffraction?
Fraunhofer diffraction can be observed if the source of light and screen at which the diffraction pattern is formed is placed at an infinite distance from the diffracting obstacle. This can be done by using two converging lenses. One lens is placed between the source of light and the obstacle while the other lens is placed between the obstacle and screen. The lens between the source and obstacle makes the rays parallel to each other while the lens between the obstacle and screen focuses the parallel rays at a point on the screen.
See Also: Interference of light
Fresnel Vs Fraunhofer diffraction
| Fresnel Diffraction | Fraunhofer diffraction |
| 1:If the source of light and screen is at a finite distance from the obstacle, then the diffraction is called Fresnel diffraction. | 1:If the source of light and screen is at infinite distance from the obstacle then the diffraction is called Fraunhofer diffraction. |
| 2:The corresponding rays are not parallel. | 2:The corresponding rays are not parallel. |
| 3:The wavefronts falling on the obstacle are not plane. | 3:The wavefronts falling on the obstacle are planes. |
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