Define Fresnel distance.
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Fresnel distance: It is the minimumdistance that a beam of light has to travel before its deviation from straight line path. Derivation: From the theory of diffraction of light for a single slit, the angle of diffraction for central maxima is.
anshpratap4010661:
this is anAn Aperture of size illuminated by a parallel beam sends diffracted beam (the central maxima) in angular width approximately . Travelling a distance , it aquires the width z λ / a due to diffraction. The distance at which this width equals the size of the aperture is called the fresnel distance. z F = a 2 / λ .
Derivation:
From the theory of diffraction of light for a single slit, the angle of diffraction for central maxima is
sinθ ≈ θ = λ/a
After travelling distance x, the half angular width of beam would become (xλ/a).
This beam width will be more than width of slit(a).
So, (xλ/a) ≥ a
=> x ≥ (a2/λ)
Here, (a2/λ) is called Fresnel distance.
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HEY AAROHI!!
HERE IS YOUR ANSWER....
An Aperture of size illuminated by a parallel beam sends diffracted beam (the central maxima) in angular width approximately . Travelling a distance , it aquires the width z λ / a due to diffraction. The distance at which this width equals the size of the aperture is called the fresnel distance.
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HERE IS YOUR ANSWER....
An Aperture of size illuminated by a parallel beam sends diffracted beam (the central maxima) in angular width approximately . Travelling a distance , it aquires the width z λ / a due to diffraction. The distance at which this width equals the size of the aperture is called the fresnel distance.
#HOPE IT HELPS..... ♥
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