When you let two fingers touch in front of your eye and but focus on the background, why does it look like they are merging or ‘building a bridge between each other’ before they physically touch?

Question

When you let two fingers touch in front of your eye and but focus on the background, why does it look like they are merging or ‘building a bridge between each other’ before they physically touch?

In: Physics

Answer 1

The phenomenon you are discussing is called Diffraction. The ELI5 is basically you are seeing your fingers touch because of the way the light is being squeezed between the tiny space.

For a more thorough explanation check out this 4 year old askscience post

When I hold two fingers together and look through the narrow slit between fingers I am able to see multiple dark bands in the space of the slit. I read once long ago that this demonstrates the wavelength of light. Is there any truth to this? If not, what causes those dark bands?
byu/jackelfrink inaskscience