Physics, asked by aarohi9274, 11 months ago

Define Fresnel distance.

Answers

Answered by kalpkawarat15

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 .

kalpkawarat15: Fresnel distance: It is the minimum distance 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

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.

Answered by naina0529

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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