X-Rays discovery

Wilhelm Roentgen was professor of physics at university of Wurzburg, Germany when he discovered X-rays in 1985. The discovery was entirely serendipitous; Roentgen was merely studying a beam of electrons in a highly evacuated glass vessel. When the electrons, moving at great speed slammed into glass wall, they produced a very high penetrating radiation - a wholly unexpected occurrence. Roentgen first noticed the radiation when it caused a paper coated with Barium Platino-cyanide to glow. The chemical compound was a standard detector of UV light which causes the chemical to fluorescence i.e. to emit visible light after it has absorbed UV light. But Roentgen's evacuated vessel was tightly covered with black cardboard and so no UV light could emerge from it. The glow must be some other kind of radiation.

When he announced the discovery of the new radiation, Roentgen wrote:

"I posesss, for instance, photographs of ............the shadow of bones of hand, the shadow of a covered wire enclosed in a box.........."

Earlier in the paper, he noted that "the darker shadow of bones is seen with in the slightly dark shadow image of hand itself.

The new radiation quickly became a diagnostic tool in hospitals all over the world. Roentgen could not determine what the rays are made of and thus rays are named as X-rays.       

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>                   

Zeeman Effect

In a magnetic field, the energy of a particular atomic state depends on value ‘m’, the magnetic quantum number. A state of total quantum number ‘n’ breaks up into several sub-states when the atom in the magnetic field and the energies are slightly more or less than energy of state in the absence of magnetic field. This phenomenon leads to splitting of individual spectral lines when atoms radiate in magnetic field. The spacing of lines depends on magnitude of fields.  

Zero Point Energy

 Energy possessed by atoms or molecules even at absolute zero.

Zeroeth Law of Thermodynamics

This law was first enunciated by R H Fowler in 1831. According to this law, when two systems A and B are in thermodynamic equilibrium with another system C, then A & B will also be in thermal equilibrium. 

Zone Plate

The optical device which verifies rectilinear propagation of light approximately by wave theory.