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:
- 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 $1: 1$.
