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Jina Song

Heisenberg’s Uncertainty Principle

Updated: Nov 20, 2022

Developed by German physicist Werner Heisenberg in 1927, the Uncertainty Principle became one of the cornerstones of quantum physics. The principle states that we cannot precisely measure both the momentum and the position of a particle simultaneously; in essence, the more precisely we know the position, the less precisely we know the momentum, and vice versa.


The equation above is the most commonly known equation regarding the Heisenberg Uncertainty Principle; the delta x refers to the uncertainty in the position (location) of a given particle, the delta p represents the uncertainty in the momentum (speed) of the particle, and the h bar is the reduced Planck constant, which is Planck’s constant divided by 2pi. Both sides of the equation must be proportional. This means that if the speed (delta x) is extremely big, the momentum (delta p) must be extremely small to maintain the proportion.


To know the accurate position of an electron requires the use of high frequency, high energy, and large momentum light that impacts the motion of the electron. Lower light energy would not impact the motion of the electron that much, and therefore the position of the electron would not be accurate. However, particles’ position can be known by combining waves to produce an interference pattern where each wavelength matches to a different energy and momentum. Therefore, this would make the momentum of the particle more unclear.

For example, if one were to take a photo of a car coming to a stop at a red light, we could know more about the car’s position and location than the car’s actual speed and momentum. However, if one were to actually measure the car’s speed over time as it drove down a road, then we would know more about the car’s momentum than its physical position.


Works Cited

Jones, Andrew Zimmerman. “Understanding the Heisenberg Uncertainty Principle.” ThoughtCo, 31 January 2018, https://www.thoughtco.com/the-heisenberg-uncertainty-principle-2699357. Accessed 20 November 2022.

“What Is the Uncertainty Principle? Heisenberg Uncertainty Principle Definition.” Caltech Science Exchange, https://scienceexchange.caltech.edu/topics/quantum-science-explained/uncertainty-principle. Accessed 20 November 2022.

“Heisenberg Uncertainty Principle - Chemistry Topics.” Google Sites, https://sites.google.com/site/chem1403/heisenberg-uncertainty-principle. Accessed 20 November 2022.


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