Question

Precise measurements of physical quantities are a need of science. For example, to ascertain the speed of an aircraft, one must have an accurate method to find its position at closely separated instants of time. This was the actual motivation behind the discovery of RADAR in World War 2. Think of different examples in modern science where precise measurements of length, time, mass etc. are needed. Also, wherever you can, give a quantitative idea of the precision needed.

Answer 1

Hint: Need for precise measurements often lead to great discoveries. RADAR is an important milestone in the history of scientific discoveries. So, most often need is the source of discovery.

Complete step by step solution:
Precise measurements of physical quantities are indeed a need for science. Exact estimation of physical quantities is crucial for the development of science.
Step 1: Mention an example where precise measurement of time is needed.
Certain physical and chemical processes demand time to be measured as an order of${10^{ - 15}}{\text{m}}$. This is made possible by sending ultrashort laser pulses having a time interval of ${10^{ - 15}}{\text{m}}$ .
Similarly, a laser distance meter (used for measuring distances) sends finely focussed laser pulses to the target and detects reflection. The interval between the two events is later converted to distance. Laser distance meters can measure distances up to $30{\text{m}}$with an accuracy of $ \pm 3{\text{mm}}$ .
Step 2: Mention an example where precise measurement of length is needed.
Protons and neutrons bind together to form the nucleus. The atom consists of the nucleus and electrons revolving around the nucleus. The nuclear radius is of the order of ${10^{ - 15}}{\text{m}}$ . The atomic radius is found out by the measuring of the distance between the nuclei of two atoms in contact. The estimation of the size of the atom requires a precision of ${10^{ - 10}}{\text{m}}$ .
Also, X-ray spectroscopy helps in determining the interatomic spacing which is of the order of ${10^{ - 10}}{\text{m}}$ in solids.
Step 3: Mention an example where precise measurement of mass is needed.
Estimation of the atomic mass led to the mass spectrograph. The mass spectrograph separates electrically charged particles in accordance with their masses. Magnetic field and electric field can be employed to deflect the charged particles and the degree of deflection depends on their masses. A mass spectrometer which is a form of the mass spectrograph is employed in measuring the masses of isotopes.

The precision required for the measurement of atomic masses by the mass spectrograph is of the order of ${10^{ - 30}}{\text{kg}}$.

Note:
Precision is considered as a measure of trueness. It determines the closeness of two measurements with each other. The measurements can be inaccurate.