Question

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Answer 1

Answer:

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Answer 2

Answer:

According to Fresnel's the entire wave front can be divided into a large number of parts of zones which are known as Fresnel's half period zones (HPZ's). The resultant effect at any point on screen is due to the combined effect of all the secondary waves from the various zones.

Suppose ABCD is a plane wave front. We desire to find it's effect at point P consider a sphere of radius (d+λ2) with centre at P, then this sphere will cut the wave front in a circle (circle 1). This circular zone is called Fresnel's first (I) HPZ.

A sphere of radius b+2(λ2) with centre at P will cut the wave front in circle 2, the annular region between circle 2 and circle 1 is called second (II) HPZ.

The peripheral area enclosed between the nth circle and (n−1)thcircle is defined as nth HPZ.

(1) Radius of HPZ : For nth HPZ, it is given by

rn=ndλ−−−√⇒rn∝λ√

Explanation:

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