Showing posts with label crystal. Show all posts
Showing posts with label crystal. Show all posts


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Critical Temperature

The highest temperature, below which a gas can be liquefied only by increasing the pressure and above which a gas cannot be liquefied how so ever high pressure may be applied.

Critical Volume

Volume of unit mass of gas at the critical temperature and critical pressure is called critical volume of gas.

Crookes Tube

A Crookes tube is an electric discharge invented by British chemist and physicist William Crookes in the early 1870’s. It consists of a sealed glass tube which is evacuated to an air pressure between 0.005Pa and 0.1Pa and incorporates two electrodes (cathode and anode) connected to external DC power supply. When high voltage is applied to the tube, electric discharge in the rarefied air inside the tube ionizes some air molecules. Positive ions move in the electric field toward the cathode and create more ions through collisions with air molecules. As positive ions strike the cathode, electrons are released from the cathode, move toward the anode in the electric field that is present between the cathode and anode.     

Cross Product

Cross product of two vectors is a vector whose magnitude is equal to the product of magnitudes of those two vectors and the sine of angle between them. Direction of this vector is perpendicular to plane containing those two vectors. 


It is defined as the probability that an event may occur when a single nucleus is exposed to a beam of particles of total flux containing one particle per unit area.


Container used to store super cooled liquids like liquid nitrogen. They are designed in such a fashion to minimize heat transfer due to radiation, conduction or convection.


Study of low temperatures less than -150 oc including production of low temperatures and behavior of materials at low temperatures is called as Cryogenics.


Instrument used to determine freezing point of a substance.


It is magnetically controlled electronic switching device that operates at extremely low temperatures. It uses principle of varying magnetic field that can cause resistance of a superconducting element to change rapidly between its high normal and low superconductive values. It is used as a switch and as a computer memory element.

Crystal Momentum

It is momentum associated with dynamical behavior of electron in periodic potential. It is defined as product of effective mass of electron and group velocity associated with electron in periodic potential.

Crystal Oscillator

Oscillations made from crystals exhibiting Piezo-electric effect. These oscillators oscillate at constant frequency which changes by less than 0.1% due to temperature and other changes.

Crystal Structure

For crystalline materials, the manner in which atoms or ions are arrayed in space is conveyed by crystal structure. It is defined in terms of unit cell geometry and the atom positions within the unit cell.

Crystal System

It is a scheme by which crystal structures are classified according to unit cell geometry. This geometry is specified in terms of relationships between edge lengths and inter-axial angles. There are seven different possible combinations of 3 edge lengths and 3 inter-axial angles referred to as crystal systems.


Material in which atoms are situated in a repeating or periodic array over large atomic distances; that is long range order exists such that upon solidification, the atoms will position themselves in a repetitive three dimensional pattern, in which each atom is bonded to its nearest neighbor atom.

Crystalline Defect

A lattice irregularity having one or more of its dimensions on order of atomic diameter is called as crystalline defect.


The state of a solid material characterized by a periodic and repeating atomic arrangement is achieved by molecular chain alignment.


A region within a crystalline polymer in which all the molecular chains are ordered and aligned is called as crystallite.

Crystallographic Direction

It is defined as vector between two points in a crystal lattice.

Curie Law

The intensity of magnetization is I=AH/T  ; ‘H’ is magnetic field strength, ‘T’ is absolute temp, ‘A’ is curies constant. It is applicable for paramagnetic substance.

Curie Temperature

The temperature above which a Ferromagnetic Material becomes paramagnetic is called as Curie temperature.


It is the unit used to describe the strength of a radioactive source in terms of number of disintegrations it undergoes in a unit time. It is designated by Ci. One curie equals 3.7 x 1010 disintegrations per second. It has originated based on rate of decay of a gram of Radium. Experiments have yielded the result that there are about 3.7 x 1010 disintegrates per second per gram of Radium. This number is taken as standard and called as Curie.

Curie–Weiss Law

The Curie law was modified by Weiss to state that susceptibility of a paramagnetic substance above the Curie point varies inversely as excess of temp above that point. This law is not valid at or below Curie point.

Current (Electric)

The net charge flowing through a crossection of a conductor in unit time is called current.

Cyclic Process

It is a process in which a system undergoes a series of changes and ultimately comes back to initial state.


Type of accelerator invented by Ernest Lawrence of university of California, Berkely, in 1932. The 1939 noble prize in physics was awarded to Lawrence for the invitation and development of the cyclotron.  Cyclotron is a particle accelerator used to accelerate charged particles using high frequency alternating voltage applied between two “D” shaped electrodes. A static magnetic field is applied perpendicularly to the plane of electrons for accelerating particles at same phase. Particles escape electrodes by traversing spiral path.

How do we define Glass?

There are number of definitions of glass which have different approaches. 

There is no universally accepted or universal definition of glass. 

It is a fusion product of materials which have been cooled to a rigid condition with out crystallization(It need not be inorganic). 

Examples of familiar glasses made from cane sugar are lollipops and cotton candy. The former are in shape of rigid block and latter are flexible fibers.

Other definitions: 

1) An Amorphous solid or glass is one in which long range order is absent and the array of equilibrium atomic positions is strongly disordered. 

2) Glass is an uncrystallized solid material. 

3) Glass is an inorganic product of fusion which has been cooled to a rigid condition with out crystallizing. 

4) A general definition including all the aspects of glass is not possible; glass is to be conceived on one hand as a physical chemical condition and on other hand as a technical material.