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a particle has a definite position and path at any given time.

at the same time, the electron is in a state where it has gone through both slits, slit A and slit B

The Observer Effect: Why Measurement MattersYou might ask, “Why does measurement cause the wavefunction to collapse? Why is observation so special?”This is one of the most perplexing features of quantum mechanics and the source of much debate. The act of measurement is what forces the system to “make up its mind” and decide which state it will occupy. The moment you measure the particle’s position or check which slit it went through, the wavefunction collapses, and the particle behaves like a classical object again—localized and definite.Without measurement, the particle exists in a quantum realm, where its position, path, and even other properties (like spin or momentum) remain uncertain and described only by probabilities.With measurement, we interact with the particle and "freeze" one of those possibilities into reality. The act of observation brings the quantum state into the classical world.This is known as the observer effect in quantum mechanics. The very act of observing or measuring a quantum system forces it into a definite state, causing the wavefunction collapse.

A proton is a subatomic particle with a positive charge and is a fundamental constituent of atomic nuclei. It is a baryon, meaning it is composed of three quarks held together by the strong nuclear force