Question

Which of the following, is the smallest unit of length?
A) Micron
B) Fermi
C) Angstrom
D) Nanometer

Answer 1

Hint: For measurement of length there are many prefixes used from highest to lowest value of measurement. For the calculation of smallest length, more is the negative power smaller will be the number. Among these options fermi is the smallest value. Tables of all the values are available for the easy calculations of bigger numbers.

Complete step by step solution:
Among the following options Fermi is the smallest value because
$1$ $fermi$ = $10^{-15} m$,
$1$ $micron$ = $10^{-6} m$,
$1$ $Angstrom$ = $10^{-10} m$ and
$1$ $nanometer$ = $10^{-9} m$

These are the prefixes used for some fixed values of SI units of measurement. This helps for the better and easy calculation of measurements having big numbers. Some units are used for large values of bigger measurements while some are used in smaller measurements. For example- to calculate the distance of a star from earth one cannot use kilometers as a unit as it will become too lengthy to calculate. So we use light years which is the distance travelled by light in one year. Similarly for calculating the radius of an electron one cannot use millimeters as it will become a very big decimal number. So to avoid such kinds of situations we use these types of prefixes.

Note: In such kinds of questions check the numerical values of the units. This will give the exact calculation of the question. To find the smallest of the values, larger the power in negative smaller will be the value. Generally all the smaller and bigger units are used for calculation of length.