Only one at a time is needed. The same is true of, say, electrons in the double slit experiment. The current through the slits can be reduced so low that only one electron at a time is passing through the slits. An interference pattern will still be produced, though you still need to accumulate many electrons at the detector over time to build up the observed pattern. After all, a single particle cannot make a pattern.Bob8102 said:If you have, say, a two-mirror interferometer that is producing an interference pattern, how many photons are interfering? Two, or just one?
Interferometry is a technique that uses the principle of interference to measure waves, including light waves. It involves splitting a beam of light into two or more paths, having those paths interact with each other, and then recombining them to produce an interference pattern. This pattern can provide precise information about the wave characteristics of photons, such as their wavelength and phase.
In theory, even a single photon can create an interference pattern if it is sent through the interferometer one at a time. The pattern emerges over time as more photons are sent through the system, each contributing to the overall interference pattern. This demonstrates the wave-particle duality of photons.
Yes, interference patterns can be observed with low-intensity light sources, including those that emit photons one at a time. Experiments with very low-intensity light, such as single-photon sources, have shown that the interference pattern still forms, although it takes longer to become visible as more photons accumulate to reveal the pattern.
Coherence is crucial for the formation of interference patterns. Coherent light sources, such as lasers, have a constant phase relationship, which is necessary for the stable and clear interference patterns. Incoherent light sources, with varying phases, produce less distinct or blurred interference patterns.
The path difference between the two arms of an interferometer determines the nature of the interference pattern. If the path difference is an integer multiple of the wavelength, constructive interference occurs, resulting in bright fringes. If the path difference is a half-integer multiple of the wavelength, destructive interference occurs, resulting in dark fringes. Varying the path difference changes the positions and visibility of these fringes.