The *double slit experiment* is a famous, albeit simple, experiment. The whole experiment can be summarized in a single picture ![[double_slit_experiment.excalidraw.light.svg]] The light emitted on the left side has to pass two slits to reach the screen on the right. The main question is what are we going to see on the screen. The experiment is used to distinguish between two main theories: a particle and a wave-theory: - **Particle Theory**: Light consists of little particles, so called light quanta or photons. These particles do not interfere and behave more or less like little balls. - **Wave Theory**: Light is a wave, it can interfere and be diffracted. The double slit experiment was used as a way to distinguish between these two alternatives. They yield very different predictions for the light pattern that we expect on the screen. Below, we can see the possible results of the experiment: ![[double_slit_particle_vs_wave.excalidraw.light.svg]] The experimental results shows that light behaves like a wave in the double slit experiment. However, in other experiments like [[Black Body Radiation|black body radiation measurements]] or the [[Photo-electric Effect|photo-electric effect]], light behaves like a particle. This behavior is sometimes called [[Wave-Particle Duality|wave-particle duality]]. In fact, it is much less mysterious, it is just an effect of [[Quantum Mechanics|quantum mechanics]]. >[!read]- Further Reading >- [[Wave]] >- [[Discreteness]] >- [[Electromagnetic Wave]] >- [[Light]] >[!ref]- References >- T. Young, I. The Bakerian Lecture. Experiments and calculations relative to physical optics, Philosophical Transactions of the Royal Society of London **94**, 1 (1804).