Given below are two statements : one is labelled as Assertion (A)… - Vidyadip

MCQ

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : The density of the copper $\left({ }_{29}^{64} \mathrm{Cu}\right)$ nucleus is greater than that of the carbon $\left({ }_{6}^{12} \mathrm{C}\right)$ nucleus.
Reason (R): The nucleus of mass number A has a radius proportional to $\mathrm{A}^{1 / 3}$.
In the light of the above statements, choose the most appropriate answer from the options given below :

A
(A) is correct but (R) is not correct
B
(A) is not correct but (R) is correct
C
Both (A) and (R) are correct and (R) is the correct explanation of (A)
D
Both (A) and (R) are correct but (R) is not correct explanation of (A)

✓

Answer

B. (A) is not correct but (R) is correct
$\quad \rho=\frac{M}{V}=\frac{m_{n} \times A}{\frac{4}{3} \pi R^{3}}=\frac{m_{n} \times A}{\frac{4}{3} \pi A R_{0}^{3}}$
So $\rho$ is almost is constant
$\mathrm{R}=\mathrm{R}_{0} \mathrm{~A}^{1 / 3}$
$R \propto A^{1 / 3}$

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