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Home > Dictionary of Science Quotations > Scientist Names Index C > Sir James Chadwick Quotes

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Sir James Chadwick
(20 Oct 1891 - 24 Jul 1974)

English physicist.


Science Quotes by Sir James Chadwick (1 quote)

If we ascribe the ejection of the proton to a Compton recoil from a quantum of 52 x 106 electron volts, then the nitrogen recoil atom arising by a similar process should have an energy not greater than about 400,000 volts, should produce not more than about 10,000 ions, and have a range in the air at N.T.P. of about 1-3mm. Actually, some of the recoil atoms in nitrogen produce at least 30,000 ions. In collaboration with Dr. Feather, I have observed the recoil atoms in an expansion chamber, and their range, estimated visually, was sometimes as much as 3mm. at N.T.P.
These results, and others I have obtained in the course of the work, are very difficult to explain on the assumption that the radiation from beryllium is a quantum radiation, if energy and momentum are to be conserved in the collisions. The difficulties disappear, however, if it be assumed that the radiation consists of particles of mass 1 and charge 0, or neutrons. The capture of the a-particle by the Be9 nucleus may be supposed to result in the formation of a C12 nucleus and the emission of the neutron. From the energy relations of this process the velocity of the neutron emitted in the forward direction may well be about 3 x 109 cm. per sec. The collisions of this neutron with the atoms through which it passes give rise to the recoil atoms, and the observed energies of the recoil atoms are in fair agreement with this view. Moreover, I have observed that the protons ejected from hydrogen by the radiation emitted in the opposite direction to that of the exciting a-particle appear to have a much smaller range than those ejected by the forward radiation.
This again receives a simple explanation on the neutron hypothesis.
— Sir James Chadwick
'Possible Existence of a Neutron', Letter to the Editor, Nature, 1932, 129, 312.
Science quotes on:  |  Neutron (7)



Quotes by others about Sir James Chadwick (1)

There was, I think, a feeling that the best science was that done in the simplest way. In experimental work, as in mathematics, there was “style” and a result obtained with simple equipment was more elegant than one obtained with complicated apparatus, just as a mathematical proof derived neatly was better than one involving laborious calculations. Rutherford's first disintegration experiment, and Chadwick's discovery of the neutron had a “style” that is different from that of experiments made with giant accelerators.
From 'Physics in a University Laboratory Before and After World War II', Proceedings of the Royal Society of London, Series A, (1975), 342, 463. As cited in Alan McComas, Galvani's Spark: The Story of the Nerve Impulse (2011), 107.
Science quotes on:  |  Accelerator (4)  |  Apparatus (18)  |  Best (42)  |  Better (41)  |  Calculation (41)  |  Complicated (14)  |  Derivation (8)  |  Discovery (360)  |  Disintegration (2)  |  Elegance (13)  |  Equipment (11)  |  Experiment (369)  |  Feeling (47)  |  Giant (15)  |  Labor (18)  |  Mathematics (367)  |  Neatness (3)  |  Neutron (7)  |  Obtain (14)  |  Obtaining (4)  |  Proof (136)  |  Result (129)  |  Sir Ernest Rutherford (30)  |  Science (875)  |  Simplicity (92)  |  Style (5)


See also:
  • todayinsci icon 20 Oct - short biography, births, deaths and events on date of Chadwick's birth.
  • book icon The Neutron and the Bomb: A Biography of Sir James Chadwick, by Andrew P. Brown. - book suggestion.

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