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Physics · 2022 · 3 marks
CBSE 2022 · Region 3 · Set 3 · Q10
(a) James Chadwick, in 1932, studied the emission of neutral radiations when Beryllium nuclei were bombarded with alpha particles. He concluded that…
(a)
James Chadwick, in $\displaystyle 1932$, 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.
(b)
Two nuclei may have the same radius, even though they contain different number of protons and neutrons. Explain.
Marking-scheme solution
a) If the neutral radiation consisted of photons then from the conservation of energy and momentum, the energy of photons would have to be much higher than the energy available from the bombardment of beryllium nuclei with $\displaystyle \alpha$ - particles. He assumed that the neutral radiation consists of a new type of neutral particles called neutron
(b)
Radius $\displaystyle R$ of a nucleus depends on mass number $\displaystyle A, R A^{\frac{1}{3}}$
Where $\displaystyle A=N+Z$
In case of Isobars mass number is same but $\displaystyle N$ and $\displaystyle Z$ are not equal.
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CBSE Class 12 Physics past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.