Showing posts with label hologram. Show all posts
Showing posts with label hologram. Show all posts

PHYSICS DICTIONARY

  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z


<Prev>                   <Next> 

Helion

Nucleus of a Helium- 3 atom consists of two protons and one neutron bound together with a total binding energy of 7.72 MeV. Helium-3 atom, a stable isotope of Helium with natural abundance of ~0.00014% consists of a nucleus (Helion) and two electrons.


Helmholtz Coil

Device introduced by German scientist Helmholtz. Device consist pair of conducting circular coils each having ‘N’ turns, and carrying a current, separated by a distance equivalent to the radius of circular loops produce a homogenous uniform magnetic field in the mid plane between two circular coils.


Helmoltz Function (or) Helmoltz’s Free Energy Function

It is thermodynamic energy function pertaining to thermodynamic process in which system exchanges heat with surrounding and there by maintains temperature constant.

Mathematically, A = A (T, V, N); A = U-TS


Henry

It is unit of inductance.


Hertz

 It is unit of frequency which is named after German physicist Heinrich Hertz.


Hertzian Wave

An electromagnetic wave produced by oscillations in electrical circuit with frequency in range 3x1010 to about 1.5x105 Hertz. They are named after Heinrich Rudolph Hertz, a German physicist.


Hetero Junction

A PN junction that encompasses two different semi conductors is called as hetero junction. The most distinctive feature of such junctions is that the P and N region have different energy band gaps.


Hexagonal Closely Packed Crystal Structure

Crystal structure having unit cell which has top and bottom faces forming regular hexagon and surround a single atom in the center. Another plane provides three additional atoms.


Higgs Particle or Higgs Boson

It is first theorized in 1964 by British physicist Peter Higgs and others, which is presumed to be basic building blocks of matter to interact. They have been confirmed to exist on 14th march 2013. The discovery of particle appears to confirm existence of Higgs field. The heavier particles interact strongly with Higgs field and light ones interact weakly with this field.


Hilbert Space

The mathematical concept named after David Hilbert generalizes notion of Euclidian space. It is an abstract vector space possessing structure of an inner product that allows length and angle to be measured.


Histogram

A histogram is graphical representation of distribution of data. It is an estimate of probability distribution of continuous variable.  It consists of tabular frequencies shown as adjacent rectangles, erected over discrete intervals, with an area equal to frequency of observations in the interval. The height of rectangle is also equal to frequency density of interval i.e. frequency divided by width of interval. The total area of histogram is equal to no. of data. 


Hole

For semiconductors and insulators, a vacant electron state in the valence bond that behaves as positive charge carrier in an electric field. A hole is not a particle and it doesn’t exist by itself.


Hologram

Consists of record of both amplitude and phase of light wave scattered from object so that it can give 3D view of the object but image cannot be observed directly from hologram because it requires reconstructing.

or

 It is counterpart of photographic negative. It consists of record of both amplitude and phase of light wave scattered from object so that it can give 3D view of the object, but image cannot be observed directly from hologram because it requires reconstructing. 


Holography

Holography dates from 1947, when British (native of Hungary) scientist Dennis Gabor developed the theory of holography while working to improve the resolution of an electron microscope. Gabor coined the term hologram from the Greek words ‘holos’ meaning "whole," and ‘gramma’, meaning "message".

Holography is "lens less photography" in which an image is captured not as an image focused on film, but as an interference pattern at the film. Typically, coherent light from a laser is reflected from an object and combined at the film with light from a reference beam. This recorded interference pattern actually contains much more information that a focused image, and enables the viewer to view a true three-dimensional image which exhibits parallax. That is, the image will change its appearance if you look at it from a different angle, just as if you were looking at a real 3D object.


Holonomic Constraints

Constraints which are expressible in the form of f(r1,r2, …..rn, t) = 0.


Homo Junction

A junction containing only one semiconductor, such as silicon PN junction, is called Homo junction. 

How does an image change in a 3D hologram depending on angle of viewing?

 A Hologram is made by taking a single coherent beam, usually from a LASER, and splitting it into two beams.

One of the beams called a reference beam, directly hits a photographic plate where as other is reflected off an object (whose image needs to be stored in the Hologram). The interference pattern of these two beams is stored as Hologram.

When light is focussed on this Holographic plate, it reflects off the plate, but after mixing with the stored pattern.

 So if the original light beam that was used is directed at the corrected angle, it cancels out the component corresponding to reference beam and we see the object.

However, in a typical room, Light hits hologram from all angles and is also reflected back in all angles. Hence, there will be a beam that will fall on plate at same angle as that of reference and reflect the image of the object. If our eye happens to be in the path of the reflected beam then we can see the stored object.

If two interference patterns were stored simultaneously with different reference beam, we can see two different images depending on the angle of viewing. Because the light reaches each eye is not exactly the same, the 3D effect or perception of depth is produced.