Discuss the work of ‘Bose-Einstein Statistics’ done by Prof. Satyendra Nath Bose and show how it revolutionized the field of Physics. (UPSC IAS Mains 2018 General Studies Paper – 3)
Satyendra Nath Bose wrote a brief article titled "Planck''s Law and the Hypothesis of Light Quanta" after adapting a lecture he gave at the University of Dhaka on the theory of radiation and the ultraviolet catastrophe.
- By treating radiation as a gas of photons (Photon gas) and using new statistical techniques for counting photon states, Bose provided a new derivation of Planck''s law.
- Einstein received a brief paper he had written on the subject and immediately recognised its importance.
- In agreement with him, Bose''s article "Planck''s Law and Hypothesis of Light Quanta" was translated by Einstein into German and published in Zeitschrift für Physik in 1924 under Bose''s name.
Bose-Einstein Statistics
Einstein generalised Bose''s works (on photons), extended it on atoms, and gave the theory of ideal quantum gas (Bose gas). This formed the basis of the Bose-Einstein statistics and Bose-Einstein condensates.
- Bose was given the opportunity to work in European laboratories for two years alongside scientists like Marie Curie and Albert Einstein as a result of this recognition.
- The new form of conceptual originality in Bose’s work was that the particles were regarded as indistinguishable, a radical departure from the assumption that underlies the classical Maxwell-Boltzmann statistics (the statistics of "distinguishable" classical particles).
- Bosons:
- It was soon realised that the new Bose-Einstein statistics were applicable only to particles with integer spins that do not follow the Pauli exclusion principle.
- The particles with integer spins are now referred to as bosons (as suggested by Dirac).
- On the other hand, Fermi-Dirac statistics are applicable to particles with half-integer spins (called fermions), satisfying Pauli’s exclusion principle.
Bose-Einstein Condensates
The pioneering ideas of Bose, developed further by Einstein, were confirmed by the observation of a new state of matter in a diluted gas of ultra-cold alkali atoms, the Bose-Einstein condensate.
- Einstein proposed that if the bosonic atoms are cooled to a very low temperature, it would cause them to condense into the lowest quantum state, thereby resulting in a new state of matter.
- Thus, Bose-Einstein condensate is a state of matter and a dense and cooled collection of bosons at a very low density, having lowest quantum state.
- This state is reached when the atoms of specific elements are cooled to a temperature close to absolute zero (0 Kelvin, or minus 273.15 Celsius).
- The atoms at this point merge into a single entity with quantum characteristics, where each particle also serves as a wave of matter.
- Experimental proof of the BECs came in 1995, as given by Eric Cornell and Carl Wieman (using rubidium atoms) and by Wolfgang Ketterle (using sodium atoms).
- All three shared the Nobel Prize in Physics in 2001.
- According to scientists, BECs hold crucial information about curious phenomena like dark energy, the unidentified energy thought to be responsible for the universe''s accelerating expansion.
- However, BECs are exceptionally fragile. They get warm post their condensation threshold with just a little contact with the outside environment.
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