How many of us study by really understanding the laws of Physics ? Not many , I guess, at least for this lovely principle. Many of us would have just swallowed syllabus and vomited them during exam, later forgetting everything like a lamb in a maze !

So, here’s an explanation for a beautifully geeky quantum mechanics theory known as ‘Heisenberg’s Uncertainty Principle’.

The principle states in plain terms as : ‘It is impossible to accurately measure the position and momentum of a particle, both at the same time’.

Do you know why both cannot be accurately measured at the same time ? Here we go :

Step 1 : Measuring Position :

Even a layman can say that to know a position of a body light is important - i.e., One cannot see or locate an object in a dark room. So, electro-magnetic energy in the form of light is needed to find the position of a particle with the naked eye. Also we know that all electro magnetic radiation including light has parameters called Wavelength and Frequency. The resolution ( or the least distinguishable distance ) that can be measured is equal to half the wavelength of the energy used ; Or in plain words we cannot use light energy to measure an object smaller than few nanometers. Whereas if we use Gamma rays which have very less wavelength ( or high frequency ) than light, we would be able to measure smaller objects.

So the Conclusion is, If we want to accurately measure an object’s position , we need to have the highest possible frequency (or lowest wavelength) of electro magnetic radiation.

Step 2 : Measuring Momentum :


We might recall from high school physics that
Momentum = Mass x Velocity ;
So it is very easy to say that for a moving particle at finite speed if you want to find the momentum at a particular instant of time then we need to have constant velocity at that instant. We know : Velocity = Rate of Change of position with time; From Step 1 we can say that to measure accurately the Rate of change of Position we need to use the highest possible frequency.

The Crunch !

One might also recall that High frequency means more energy from the intermediate school physics equation :
E = h x v ; where h - Planck’s Constant and v - frequency. So if we use high frequency electromagnetic radiation it means we are using high energy radiation. As we are concerned of quantum scale particles, their inherent velocity will get boosted up when you use high energy .i.e., We would inadvertently change the position of the particle which contradicts our Step 1.

Position and Momentum are mutually exclusive to each other!

Thus if low frequency ( larger wavelength ) is used, then the particle would not get shifted from its position while measuring but alas - the resolution of measuring or accuracy gets down due to the increase in wavelength ! This is why velocity and momentum cannot be accurately measured at the same time!

I guess this is simple enough to understand. If you’ve got any questions, please feel free to login to Space Boy Forum right away !

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