>>14358994When stuff that behaves like a wave (ex. sound waves, shock waves, water waves, etc.) approaches an obstacle with characteristic features that are small compared to the wavelength, the waves diffract - they bend around corners, ripple out after crossing through gaps, etc. These diffracted waves can interfere with each other, producing predictable interference patterns.
The same thing happens when you shine light through very tiny slits - the light diffracts through the slits, interferes with the rest of the diffracted waves, and produces an interference pattern - this experimental evidence affirms that light has wave-like properties. Other experimental evidence, like the photoelectric effect on the other hand, implies light has particle-like properties. The conclusion is that light behaves like both a wave and a particle.
Where things get weird is that if you do the same with something we normally think of as only a particle (like an electron) you get the same behavior - interference patterns forming in the detection of electrons passed a pair of narrow slits. These same patterns appear even if you shoot the electrons through one at a time. Matter, like electrons, protons, neutrons, etc. also can behave like both a wave and a particle.
