PHYSICS DICTIONARY

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Hall Effect
When a piece of semiconductor carrying a current is placed in a transverse magnetic field, an electric field is produced inside the conductor in a direction normal to both current and magnetic field.

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

Heat
It is a form of energy (kinetic energy of molecules constituting the body) which produces sensation of warmth.

(or)

It is energy that is transferred between a system and its environment because of a temperature difference that exists between them.

Heat engine
It is a device involving cyclic process in which heat is continuously converted into mechanical work.

Heliocentric theory
Theory proposed by Copernicus as per which all the planets revolve round the sun.

Hamilton’s principle
If a particle moves from one point to other in time interval t1 ≤ t ≤ t2 then the actual path it follows is the one for which action assume stationary value.

Humphrey series
Spectrum of wavelength formed due to jumping of electrons from higher orbits to sixth orbit. The spectrum falls in far infra red region.

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

Heat capacity
Amount of heat required to raise the temperature of whole body of mass M through one degree centigrade or one Kelvin.

Hoppers
The materials in which hopping conduction takes place. They are also called electron transfer materials.

Hydrogen bond
The bond occurs between molecules in which one end is a hydrogen atom. The hydrogen atom is covalently bonded to a relatively large atom such as Nitrogen, Oxygen or Fluorine to form a permanent dipole.

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.

Hooke’s law
As per this law, for most metals that are stressed in tension and at relatively low levels, stress & strain are proportional to each other.

Hardness
Mechanical property which is a measure of materials resistance to localized plastic deformation.

Hole
For semiconductors and insulators, a vacant electron state in the valence bond that behaves as positive charge carrier in an electric field.