Question

Which of the following is the smallest unit?
(A). Millimetre
(B). Angstrom
(C). Fermi
(D). Meter

Answer 1

T Write all those given in terms of 10 to the power and meter , which is standard unit for distance measurement and then compare to arrive to the correct answer.

Complete step-by-step answer :
The unit of the physical quantity is used for measuring the magnitude of the quantity. There are three types of units:
Fundamental units: These units are the base units. Length, mass, time, temperature, current, amount of substance and luminosity are the seven fundamental quantities of the system. The units of these quantities are known as the fundamental units.
Supplementary units: The supplementary physical quantities are the quantities which are dimensionless. There are two supplementary units: radian and steradian.
Derived Units: The units that are expressed in terms of the fundamental quantities are known as the derived units.

The meter is the SI unit of the length.
1 millimetre = $\dfrac{1}{{{10}^{3}}}$ metre
1 angstrom = $\dfrac{1}{{{10}^{10}}}$ metre
1 fermi = $\dfrac{1}{{{10}^{15}}}$ metre

So, comparing the above units with the SI unit of length. The fermi is the smallest unit of the length.
Hence the correct option C

Note : For comparison of the units SI system is considered. The SI system of units is the internationally accepted system of measurement of units. This system is used to avoid the communication gap in different parts of the world.