Question

The nuclear size is measured in the units of
a) Angstrom
b) Fermi
c) Bar
d) light year

Answer 1

Hint: The nuclear size refers to the size of the nucleus of an atom. The diameter of an atom is found to be of the order of ${{10}^{-10}}$. Hence the size of the nucleus will be even smaller than this. To come up with an answer to the above question we need to manipulate the incorrect options among those provided by knowing what they mean and are they suitable enough to measure the nuclear size.

Complete step-by-step solution:
To begin with, let us define each of the following terminologies provided to us in the options.
Angstrom is the unit used to measure the physical quantity which has an order of ${{10}^{-10}}$. In the above hint itself, we mentioned that the size of an atom itself is of the order ${{10}^{-10}}$ and hence angstrom is not suitable to measure the nuclear size.
The bar is the unit of pressure. But concerning the nuclear size we want a unit that can be used to measure the distance. Hence the bar cannot be the unit of size, as for the matter of anything.
A light-year is a unit used to measure the distance between the planets in the solar system. 1 light-year is the distance traveled by the light in one year. This distance is very huge as compared to the nuclear size and hence is not suitable for measuring the nuclear size.
Fermi is a unit of the order ${{10}^{-15}}$. The size of the nucleus is estimated to be around of the order ${{10}^{-14}}$. Hence Fermi can be used to express the nuclear size of an atom.
Hence the correct answer is option b.

Note: A nucleus is basically located at the center of an atom. An atom as a whole consists of protons, electrons, and neutrons where the number of electrons is equal to the number of protons. Since electrons are negatively charged protons are positively charged and neutrons having no charge, an atom is electrically neutral. Whereas a nucleus is positive in nature because it comprises the protons and the neutrons.