Physical Concept of Uncertainty Principle

To determine the position of an object, we must be able to see the object. This can be done with the help of light of suitable wavelength. When a beam of light falls on an object, the photons of this incident light are scattered by the object and the reflected light enters our eye. Now, if the object is large, its position and velocity will not change by the impact of the striking photons. Thus, it will be possible to determine both the position and velocity of the object simultaneously.

However, in case of microscopic objects, such as electrons, the interaction of the striking photon of light with the particle will cause appreciable displacement of the particle from its normal path. As a result of this, the particle undergoes a considerable change in its path and velocity (or momentum) due to the impact of a single photon used to observe it. Thus, the very act of measuring the position of the microscopic particle causes a change in its momentum.

fig 1.1 - The change in the path of electron by the impact of striking photon

The above figure shows as to how the position of an electron changes by the impact of photon. The collision of photon with the electron sends it in an unpredictable direction. Thus, it is not possible to determine simultaneously the exact position and momentum of the electron or of any other microscopic object.