Asked By
reema
70 points
N/A
Posted on - 10/08/2011
What is meant by Fresnel distance in optics IE diffraction how is it related to the validity of ray optics please do make it simple as I am a beginner?
Answered By
Ealdwine
10 points
N/A
#89616
What is meant by Fresnel distance in optics
The Fresnel diffraction in optics is expressed by an equation for near field diffraction and it is an approximation of Kirchhoff-Fresnel diffraction which can be employed to the propagation of waves in the near field.
The near field is denoted by the Fresnel number, F of the optical arrangement that can be defined as for a wave incident on an aperture:
-
where
-
is the characteristic size of the aperture
-
is the distance of the observation point from the aperture
-
is the wavelength of the wave.
The several Fresnel diffraction causes the specular reflection at the nearly placed periodical ridges and this result may be employed for atomic mirrors.