A curious observer’s guide to quantum mechanics, pt. 3: Rose colored glasses - Ars Technica

This is the first time we’ve seen stripes slowly disappear; in our previous examples, the stripes were either there or not.

We can tentatively associate this fading of the stripes as we change the path length with the length of the photon traveling down the path.

By measuring how far until the stripes disappear, we have measured the length of the particle’s wave ripples.

But now we can also measure how the stripes behave as we adjust the path length.

While we often use lasers to generate particles of light (they are great photon pea shooters), any kind of light will do: an incandescent light bulb, an LED room light, a neon lamp, sodium streetlights, starlight, light passed through colored filters.

Whatever kind of light we send through creates stripes when the path lengths match.

But the stripes fade away at distances that range from microns for white light to hundreds of kilometers for the highest quality lasers.

Some of the light sources have a very narrow range of colors (the laser light, the neon lamp, the sodium streetlight); some have a wide rainbow of colors (the incandescent bulb, LED room light, starlight); while others such as sunlight sent through a colored filter are intermediate in the range of composite colors.

What we notice is that there is a correlation: the narrower the color range of the light source, the longer the path difference can be before the stripes disappear.

If I choose a red filter and a blue filter that allow the same width of colors through, they will have their stripes disappear at the same path difference.

Which brings us to a rather startling result: the length of a particle wave is given by the range of colors (and thus energies) it has.