Modern Physics 5 Question 4

4. X-rays are incident on a target metal atom having 30 neutrons. The ratio of atomic radius of the target atom and ${ } _2^{4} He$ is $(14)^{1 / 3}$.

$(2005,4 M)$

(a) Find the mass number of target atom.

(b) Find the frequency of $K _{\alpha}$ line emitted by this metal.

$$ \left(R=1.1 \times 10^{7} m^{-1}, c=3 \times 10^{8} m / s\right) $$

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Answer:

Correct Answer: 4. (d)

Solution:

  1. Mass density of nuclear matter is a constant quantity for all elements. It does not depends on element’s mass number or atomic radius.

$\therefore$ The ratio of mass densities of ${ }^{40} Ca$ and ${ }^{16} O$ is $1: 1$.



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