Tuesday, 31 January 2017

Notes on Atomic and nuclear Physics

Atomic and Nuclear Physics

Cathode Rays

Cathode rays, discovered by Sir William Crooke and its properties are
  • travel in straight lines.
  • Produce fluorescence.
  • can penetrate through thin foils of metal and deflected by both electric and magnetic fields.
  • have velocity ranging 1/30th to 1/10th of the velocity of light.

Positive or Canal Rays

  • These rays were discovered by Goldstein.
  • The positive ray consists of positively charged particles.
  • These rays travel in straight line.
  • These rays are deflected by electric and magnetic fields.
  • These rays can produce ionization in gases.


  • X-rays are electromagnetic waves with wavelength range 0.1 A-100 A.
  • X-rays were discovered by Roentgen.
  • X-rays travels in straight line.
  • Long exposures of X – rays in injurious for human body.
  • X – rays shows photoelectric effect.
Uses of X-Rays
  • In medical sciences X-rays are used in surgery for the detection of fracture, diseased organs, foreign matter like bullet, stones etc. They are used in treatment of cancer and in skin diseases.
  • In Engineering, X-rays are used in detecting faults, cracks, flaws and gas pockets in the finished metal products and in heavy metal sheets.
  • In Scientific Work, X-rays are used in studying crystal structure and complex molecules.
  • In Custom Department X-rays are used in custom department for detection of banned materials kept hidden.


  • Radioactivity was discovered by Henry Becquerel, Madame Curie and Pierre Curie for which they jointly won Nobel Prize.

Nuclear Fission

  • Atom Bomb is based on nuclear fission. U235 and Pu239 are used as fissionable material.
  • Nuclear fission was first demonstrated by Halin and Fritz Strassmann.

Nuclear Fusion

  • When two or more light nuclei combined together to form a heavier nucleus is called as nuclear fusion.
  • For the nuclear fusion, a temperature of the order of 108 K is required.
  • Hydrogen Bomb was made by the American Scientist in 1952. This is based on nuclear fusion. It is 1000 times more powerful than atom bomb.

Nuclear Reactor or Atomic Pile

  • Nuclear reactor is an arrangement, in which controlled nuclear fission reaction takes place.
  • First nuclear reactor was established in Chicago University under the supervision of Prof Enrico Fermi.
  • Heavy water, graphite and beryllium oxide are used to slow down the fast moving neutrons. They are called moderate.
Uses of Nuclear Reactor
(i)To produce electrical energy from the energy released during fission.
(ii)To produce different isotopes, this can be used medical, physical and agriculture science.
There are several components of nuclear reactor which are as follows:
  • Fissionable Fuel U235 or U239 is used.
  • Moderator decreases the energy of neutrons, so that they can be further used for fission reaction.
  • Heavy water and graphite are used as moderator.
  • Control Rod rods of cadmium or boron are used to absorb the excess neutrons produced in fission of uranium nucleus, so that the chain reaction.