# Out of phase light/photons, would it be measurable?

• rolls
In summary, it is possible to create co-propagating waves out of phase so that they cancel out, however this is not possible with light as it does not interact like sound does.
rolls
With sound you can create out of phase signals and they cancel out, this is not possible with light as it does not interact like sound does.

If it was possible to create two light sources in that were exactly 180 degrees out of phase with each other and aim them at a common point (eg an isosceles triangle, the two points of identical angle are the light source, the 3rd point is the measurement point) regardless of the distance from the source to the point on which they combine the wavelengths would appear to cancel would they not? If they were of identical frequency and amplitude they would never depart from each other and would continue to appear "cancelled" at every point of measurement despite the photons still being there and containing energy.

The light would not be coherent until the meeting point, this is the point upon which you would attempt to measure the frequency/amplitude. Would it appear to be zero?

How would you actually produce an experiment like this, eg how could you lag the phase of a light signal, does it even make sense to attempt something like that?

The reason for the question is I'm wondering if you could hide the fact a device/experiment is releasing energy by making all measurements appear null.

rolls said:
would continue to appear "cancelled" at every point of measurement despite
No, if you have destructive interference at one location then you will have constructive interference at another location.

The geometry you describe is the standard geometry for a double slit experiment. But with the regions of constructive and destructive interference swapped.

Interference like you describe is not difficult with light. The very thing you describe: creating co-propagating waves out of phase so that they cancel everywhere is exactly how dielectric mirrors work. Overlapping multiply reflected beams traveling forward cancel everywhere, so the beam has no choice but to reflect. Actually the interference is constructive for the reflected beam. As Dale points out, this is a fundamental principle. The energy can't just disappear. No arrangement of interference can make the beam eliminate itself. What's lost in destructive interference has to show up somewhere in constructive interference.

The case you describe of bringing beams together at an angle to interfere at an overlap point is how polar illumination in a photolithography machine makes the nm scale features on your computer chip. However due to the angle you don't get cancelation across the focal plane. You get modulation. Technically interference is how all photography and in fact all optics work.

There are examples of light engineering for interference all around. Iridescent paint, the diffractive optic element on your laser pointer that makes a funny shape, the hologram on your credit cards.

rolls said:
With sound you can create out of phase signals and they cancel out, this is not possible with light as it does not interact like sound does.

Er...yes it does!

Send a beam into an interferometer, adjust one arm of the interferometer so that you get a destructive interference, and voila!

Zz.

## 1. What is out of phase light?

Out of phase light refers to light waves that are not in sync with each other. This can happen when light waves of different frequencies or wavelengths interfere with each other.

## 2. How can out of phase light be measured?

Out of phase light can be measured using specialized equipment, such as a Michelson interferometer or a Fabry-Pérot interferometer. These instruments can detect changes in the phase of light waves and determine if they are out of phase.

## 3. What causes light to become out of phase?

Light can become out of phase when it is reflected or refracted through different mediums, such as air, water, or glass. It can also occur when light waves interact with each other, such as in interference or diffraction.

## 4. Is out of phase light a common occurrence?

Yes, out of phase light is a common occurrence in many natural and artificial environments. It can be observed in everyday phenomena, such as rainbows, oil slicks, and soap bubbles.

## 5. Can out of phase light have practical applications?

Yes, out of phase light has practical applications in various fields, including optics, telecommunications, and imaging. It can be used to manipulate and control light waves for various purposes, such as creating holograms, improving resolution in microscopy, and enhancing communication signals.

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