## What is far-field diffraction?

In optics, the Fraunhofer diffraction equation is used to model the diffraction of waves when the diffraction pattern is viewed at a long distance from the diffracting object (in the far-field region), and also when it is viewed at the focal plane of an imaging lens.

What is the Fresnel approximation?

In optics, the Fresnel diffraction equation for near-field diffraction is an approximation of the Kirchhoff–Fresnel diffraction that can be applied to the propagation of waves in the near field.

What is Fraunhofer diffraction explain it briefly?

Fraunhofer diffraction is the type of diffraction that occurs in the limit of small Fresnel number . In Fraunhofer diffraction, the diffraction pattern is independent of the distance to the screen, depending only on the angles to the screen from the aperture.

### What is the difference between near-field and far-field diffraction?

Diffraction phenomena have been classified into two regimes, i.e., near-field and far-field diffraction. Near-field effects rely on Fresnel diffraction, whereas far-field effects are based on Fraunhofer diffraction.

What is near field and far-field in optics?

An oscillating electric dipole (e.g. an antenna or an excited atom or ion) emits electromagnetic radiation. Here, the near field has an extension less than one wavelengths. The far field occurs for distances from the dipole which are much larger than the wavelength.

Where does far-field start?

It is widely stated in the antenna literature that the far field of an antenna operating in free space, where all the aforementioned properties must hold, starts from a distance of 2D 2 /Λ, where D is the maximum dimension of the antenna and Λ is the operating wavelength.

#### What is meant by paraxial approximation?

In geometric optics, the paraxial approximation is a small-angle approximation used in Gaussian optics and ray tracing of light through an optical system (such as a lens).

What is Fraunhofer diffraction and Fresnel Diffractlon?

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 is far field in optics?

The far field is the region far from the focus, with a distance much larger than the Rayleigh length, where the beam radius increases about linearly with the distance from the focus.