Why is it called half period zone?

The secondary wavelets from any two consecutive zones reach P with path difference ��/2 or time difference T/2 half period. That is why the zone are called fresnel’s half period zone.

What are half period Zones answer?

The area enclosed between O and O1, O1 and O2, O2 and O3 etc. are known as half period zones. Each zone differs from its neighbour by a phase difference of π or a path difference of λ/2. The area enclosed by the first circle of radius OO1 is called the first half period zone.

What will be the difference between two consecutive zones in case of Fresnel’s half period zone?

The phase difference is thus $\pi$ between each successive half period zones of strips. So, the correct answer is option C.

How the radius of the half period zones depends on the wavelength?

Therefore, the radii of the zones are proportional to the square root of natural numbers. Thus the area of each half period zone is same and is equal to λ . Also, the area of any zone is directly proportional to the wavelength (λ) of light and the distance of the point from the wavefront (b).

What is Zone Plate physics?

A zone plate is a device used to focus light or other things exhibiting wave character. Unlike lenses or curved mirrors, zone plates use diffraction instead of refraction or reflection. Based on analysis by French physicist Augustin-Jean Fresnel, they are sometimes called Fresnel zone plates in his honor.

What is the area and radii of half period zones?

Explanation: We know that the formula for the radius of half period zone =\sqrt{nb\lambda}, where n is a natural number. Thus, it is proportional to the square root of wavelength light and inversely proportional to the square root of the frequency of light. 6.

What is the basic difference between Fresnel and Fraunhuffer diffraction in term of wavefront?

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 are the factors on which the amplitude of light waves from a half period zone at the point of observation depend?

The amplitude of the wavelet at the point O depends on the following factors: (1) The amplitude at the point O is directly proportional to the area of the zone. (2) The amplitude falls off inversely as the square of the distance of the zone from the point O.

What is half period Strip?

The half period zone is provided by an optical device known as zone plate. It is simply a plane parallel gloss plate having concentric circles of radii accurately proportional to the square roots of the consecutive natural numbers 1,2,3 etc. The area is given by πγ2. Hence the.

What are Fresnel’s half period zones?

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.

Why is the path difference called a half period?

Since when you consider two rays,one from the top and the other from the bottom of the zone which reach the screen,there is a path difference of λ/2 between them which is equivalent to half period. It’s so called because the resultant amplitude at any point becomes half of the amplitude due to the first zone.

Why is a zone plate called a half period?

It is called half period because light reaching to observation point from each of that zone has period of π which is half of full period i.e 2π so called half period zone plate.. in case of zone plate we use black paint to cover alternative zones so that period became 2π so called zone plate or full period.

What are Fresnel zones in diffraction?

In the study of Fresnel diffraction it is convenient to divide the aperture into regions called Fresnel zones. Figure 1 shows a point source, S, illuminating an aperture a distance z1away. The observation point, P, is a distance to the right of the aperture.