Nature of Physics Laws

The method by which we study matter, energy and their mutual interaction so as to formulate the laws and theorems in physics, is called the technique of physics or the scientific method. Thus, the systematic, step-wise and logical approach, adopted by the scientists for their research work, is called the scientific method.

Various steps of scientific method

Following are the main five steps of scientific method :

Systematic observations
Formation of hypothesis
Testing the validity of hypothesis
Formation of principle, and
Formation of law.

(i) Systematic observations-To find the solution of a problem, first the scientist performs well planned experiments and collects data related to that problem by taking the systematic observations.

(ii) Formation of hypothesis—To explain the data obtained from experiments, he then forms a working principle which is called the hypothesis.

(iii) Testing the validity of hypothesis—On the basis of above hypothesis so formed, some conclusions are drawn and then some predictions are made which are then verified by performing the new experiments.

(iv) Formation of principle-If the conclusions and predictions get verified by the experiments, the hypothesis is given the form of the principle, otherwise that hypothesis is modified and a new hypothesis is made which after the testing of its validity, is given the form of a principle. Thus a hypothesis is first tested through experiments and then it is called a principle.

(v) Formation of law- The principle so established is generally true only for some limited phenomena, observations and facts. However, if the principle so propounded is found to be true for all the phenomena, observations and facts, it is given the form of a law. Otherwise, the principle is modified and then a new principle is given which after testing the validity, given the form of a law.

It may be mentioned here that changes can be made in a principle, but no changes can be made in a law. Sometimes, an established principle may not agree with the new observation or new principle, then that principle is not completely discarded, but is amended or modified.

For example, to explain the formation of shadow of an obstacle by light, it was assumed that light travels in a straight line and the rectilinear propagation of light was then explained by the Newton's corpuscular theory. But Newton's corpuscular theory could not explain the phenomenon of diffraction of light at a straight edge. Then Huygen's wave principle of light was propounded. Wave principle of light could successfully explain interference, diffraction, polarisation etc., but this principle could not explain the photoelectric effect. For this, Planck propounded the quantum principle of light. Later on, de Broglie gave the wave-particle hypothesis, according to which each moving particle is associated with a wave. On this basis, the quantum principle of light could successfully explain all the phenomenon of light.

We find following facts regarding the nature of fundamental laws of Physics propounded by the scientific method described above.

(1) All fundamental laws of Physics are universal in nature and they can be applied in general, in each circumstances and reference.
(2) Physics has its wide field of application. Here we study from the smallest particle, say electron (size = 10-14 m, mass = 10-30 kg) to the biggest body, say galaxy (size = 1026 m, mass – 1055 kg).reference.
(3) In nature, there are four basic forces : (i) gravitational force, (ii) electromagnetic force, (iii) strong nuclear force and (iv) weak nuclear force. These forces control the various activities of macro and micro systems.

(4) There are some physical quantities which do not change with time in a physical phenomenon. Such quantities are called the conserved quantities. The laws of Physics related to such quantities are called the laws of conservation.

Some conservation laws are : law of conservation of mass, law of conservation of mechanical energy, law of conservation of energy, law of conservation of linear momentum, law of conservation of angular momentum, law of conservation of charge etc. These laws of conservation are based on observations and experiments. None of the conservation law can be verified, but that can be established or discarded by experiments.