Modern Physics: Chapter 3 – Making (Non)Sense of the Double Slit Experiment

So let’s get this straight. An electron gives a wave-life diffraction pattern in the double slit experiment. It clearly shows wave behavior. However, as soon as you put detectors in front of the slits and try to detect the electron, its pattern changes to a bullet-like particle pattern. So is an electron a wave or a particle? Well… it’s both and neither.

Wave-Particle Duality

What we have understood till now is that an electron seems to behave like a way till it gets detected. After detection it behaves like a particle. A workable hypotheses might be to consider an electron (and everything else) as both a wave and a particle. A question arises, though. We already know how to calculate the particle properties of the electron such as momentum ( p = mv ), but if it’s a wave, how do we calculate its wavelength?

Matter Waves

The French Physicist, Louis de Broglie postulated that the wavelength of the ‘matter wave’ associated with a particle (such as an electron, proton or even you, me, the earth, Jupiter and chickens) can be calculated using the following relation:

  • \lambda = \frac{h}{p}

where \lambda is the wavelength of the associated matter wave, p is the momentum and h is what’s called the Planck constant.


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