This function doesn't exist. So why is it everywhere in physics?

The Dirac delta function is one of the most useful—but also, most commonly misunderstood—mathematical objects used throughout physics, engineering, and applied math.

In this lesson, I'll teach you the physical intuition behind the delta function, as well as its more precise formulation using the mathematical theory of distributions. We'll also discuss five key applications where the delta function plays an essential role:

  • The density function for a point-like mass or electric charge

  • The impulsive force from a mechanical collision

  • Gauss's law for the electric field of a point charge

  • The Fourier Transform of a constant function

  • The wavefunction of a quantum particle at a definite position

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