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.