How big is a visible photon?

The script introduces the complex nature of defining the size of a photon, a particle of light. It discusses the traditional view of photons as tiny entities and contrasts it with the need for them to be large enough to interact with objects like slits in the double-slit experiment. The author reflects on the changing understanding of photons, noting the lack of a definitive answer to their size and the debate around whether they occupy space. The script also touches on the concept of wavelength versus size and the human tendency to associate size with physical objects, leading to the complexity of understanding light's behavior.

This paragraph delves into the properties of light, particularly its interference patterns observed in experiments like the double-slit experiment. It discusses the electromagnetic nature of light and the common visualization误区s of electromagnetic fields. The script points out that these fields are not as localized as often depicted and questions the traditional understanding of photons as localized entities. It also explores the quantized nature of light detection, where energy is removed in discrete amounts, and the paradox of a widely distributed field being detected locally.

The author recounts a modified double-slit experiment conducted in 2020 that challenged their previous understanding of photons. By creating two spatially separated paths with a significant length difference and observing interference at a 'single photon' level, the experiment suggests that a single photon can take multiple paths simultaneously over large distances. This finding contradicts the local electromagnetic wave model and leads the author to reconsider their explanation for this phenomenon, hinting at a need for a new understanding of light's behavior.

The script describes the experimental setup for observing single photon interference, including the use of a HeNe laser, beam splitters, and a camera for detection. It discusses the process of attenuating the laser beam to single photon levels using gray filters and the challenges of ensuring the experimental conditions are suitable for detecting such low light levels. The author reflects on the results of the experiment, which show clear interference patterns even with a significant path length difference, leading to a deeper contemplation of the nature of light and the limitations of their initial explanation.

In this paragraph, the author explores the concept that the electromagnetic field of light, even when attenuated to low intensities, remains continuous and coherent. They explain that the field's ability to be split and attenuated does not affect its coherence, which can explain the observed interference patterns. The script corrects a previous misconception, noting that the experiment's results were not due to single photons but rather the continuous nature of the field. It also touches on the statistical variations in photon detection, known as shot noise, and the implications for understanding the quantization of light.

The final paragraph synthesizes the discussion on the nature of photons, proposing that they can be viewed as both a continuous electromagnetic field and as localized interactions with matter. It emphasizes the lack of a fundamental limit to the size of the field's interaction and contrasts this with the extremely localized phenomenon of photon detection. The author reflects on the difficulty of reconciling the wave-like spread of energy with the localized and quantized energy transfer during detection, inviting the audience to consider the complex dual nature of light.