Heisenberg’s Uncertainty Principle


Heisenberg’s Uncertainty Principle

Now with the wave nature associated with the moving electron it became increasingly difficult to locate an electron inside the atom and calculate its velocity. A particle occupies a particular location but a wave is spread out in a region. Because of their wave properties electrons are always spread out rather than located in a particular place. We think that objects must be located in their precise location, for example, books on shelf etc. Same thinking goes into the location of tiny particles like electrons.
According to Newton, everything in the universe can be perfectly measured. That is if we determine the location and velocity of a body then we can always predict the future course of that body in the Universe. Viewing electrons and other particles as “Particle Waves” which are highly de-localised changes the way we see universe. Instead of things having exact location and motion they are distributed in some region in space. Heisenberg proposed that locating an electron and determining its velocity, both cannot be done simultaneously and accurately because of the wave characteristic of electron. To locate an electron we will have to use a radiation and this radiation will change the energy of the electron and will disturb its location and velocity. That means electron is highly sensitive to these changes. And that is why this principle holds true.

“It is impossible to determine the position and momentum of an electron simultaneously and accurately.”

The more accurately we know the position, the more “uncertain” we are about the motion. Heisenberg’s Principle forever changed our way of thinking. These Uncertainties are diminished in the macroscopic world but at the scale of electrons, protons etc this is highly profound. The conclusion is, we cannot locate an electron around the nucleus as a particle, and we can only talk about possibilities of it being at a location. Heisenberg also gave a relationship between uncertainty in position and momentum of a particle wave.
x × p h/4p
Where x and p represent the uncertainties in position and momentum respectively. We can clearly see if uncertainty in position is zero that is position is determined accurately then the uncertainty in momentum becomes indefinite and vice-versa. It can be shown that uncertainties for macroscopic particles are very small as compared to their dimensions.



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