If you shine a flashlight through a narrow slit, the wall won't show a thin stripe but a blurry patch. Light simply cannot pass through tight spots without spreading. That's why you can't get a light spot smaller than half the wavelength of light.
When light passes through these two slits, waves of electrons ripple across the silver surface. These waves push the light from both sides and squeeze it, like palms pressing a stream of water. As a result, a line of light forms behind the plate that is twice as thin as the previous limit. And this line doesn't hug the surface; it flies onward like a narrow beam.
Previously, it was thought impossible: if you squeeze light harder than usual, it would immediately die out at the surface. Now it's shown that you can both squeeze it and send it far away. This could help make smaller features in electronics, pack more data onto a disc, and see tiny objects under a microscope.
Diffraction was first described by Leonardo da Vinci in the 15th century, and a precise description was given by Francesco Grimaldi in the 17th century. The slit width in the simulated lens (80 nm) is almost 8 times smaller than the wavelength of light (633 nm).