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Question
James Chadwick, in 1932 studied the emission of neutral radiations when Beryllium nuclei were bombarded with alpha particles. He concluded that emitted radiations were neutrons and not photons. Explain.
Solution
In 1932 James Chadwick observed the emission of neutral radiation when beryllium nuclei were bombarded with alpha-particles. It was found that this neutral radiation could knock out protons from light nuclei such as those of helium, carbon and nitrogen. The only neutral radiation known at that time was photons. Application of the principles of conservation of energy and momentum showed that if the neutral radiation consisted of photons, the energy of photons would have to be much higher than is available from the bombardment of beryllium nuclei with α-particles. So, Chadwick assumed that neutral radiation consists of a new type of neutral particle called neutrons.
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