| James Chadwick | | Date Created: Sep 19, 2004, 07:05 PM |
| On December 12, 1935, James Chadwick delivered his Nobel address after receiving his Nobel Prize in Physics for the discovery of the neutron. Chadwick's presentation address and short biography are available at the official historical site of the Nobel Prize. |
 I will discuss Chadwick's Nobel Lecture during our next class. It is a wonderful lecture that illustrates scientific discovery and the physics of radiation's passage through matter.
The lecture begins by comparing the interaction of the neutron with hydrogen and with nitrogen. Of course, Chadwick did not know what the neutron was and certainly not its mass. But, by measurint the maximum velocity that can be imparted to each gas, he was able to estimate the neutron's mass.
Next, he discusses the neutron's range. A neutron "can pass easily through a thickness of matter, e.g. 10 or even 20 cm of lead." If the neutron was charged, it's range would be much shorter. Thus, the neutron is a neutron particle.
Finally, Chadwick discusses beta decay, the elastic and inelastic interaction of neutrons with other nuclei, the deuteron, and nuclear structure. Having discovered the true constiutiants of the nucleus, physicists were finally able to describe the forces that hold the nucleus together and explain why the neutron is stable.
Remarkable. |
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