What would the properties of an infinitely long wavelength of light be? And what about a wavelength of light that is infinitely short? What would that look like?
edit: light as in electromagnetic waves, not visible light. Sorry if it was not very clear
A wave with an infinitely long period isn’t really recognizable as a wave. It’d just be interpreted as a flat line anywhere in the universe. And as mentioned, the energy of light is tied to its frequency:
E = hf. (Or with hbar • omega, but that’s just multiplied with and divided by 2π, so, the same thing.)So an infinitely long wave would have f=0 and thus no energy.
The highest frequency you’d get would be 1/planck-time, so the energy would be the Planck constant divided by Planck time, which would be roughly 12.3 GJ. That’s a lot of energy for just one photon, but if it’s just the one, likely not world-ending.
I really love when physic estimates end with “probably not world ending”
Now do the shortest possible wavelength. World-ending yes or no?
If I’m not mistaken, their last paragraph describes this to contrast the answer above about the longest (I.e. lowest) frequency.
If it’s infinitely long it has zero energy, making it kind of irrelevant.
Wouldn’t f=0 describe any place of equilibrium in the electromagnetic field? Anywhere there isn’t currently a photon?
I mean, the expansion of the universe is a wave propagating with a potentially infinite wavelength. Not necessary for it to be any light stretching from the beginning of the universe, but also not impossible afaik.
The wave would probably interact weakly with anything making it very hard to detect. And depending on the initial burst it will probably also have it’s energy too spread out to be of any noticeable amplitude.
I think your terminology is a bit mixed up. Light is a subset of the electromagnetic spectrum that we can see, plus infrared and UV often also being referred to as “light”.
As for the properties, they don’t fundamentally differ across the spectrum. The longer the wavelength, the less energy and the shorter the wavelength, the more energy.
As for the shortest theoretically possible wavelength, we are probably in the area of a Planck length
The Planck length is about 10-20 times the diameter of a proton.
Light is a subset of the electromagnetic spectrum
No, it’s not. In physics, we call the entire spectrum “light”, because it’s all fundamentally the same thing.
We can talk about “visible light”, but that’s a subset of light in general. Microwaves, radio waves, x-rays, gamma radiation, and any other section of the spectrum you can think of are all light
https://en.wikipedia.org/wiki/Light
Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye.[1] Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively optical radiation.[2][3]
In physics, the term “light” may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not.[4][5] In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization. Its speed in vacuum, 299792458 m/s, is one of the fundamental constants of nature.
I didn’t know that some physicists choose such confusing terminology. Electromagnetic radiation is the more clear term and i have learned it as such in school, e.g. light being a part of the electromagnetic spectrum and generally speaking of electromagnetic radiation rather than light.
Cause things get named CENTURIES before we understand them, and as we learn more, sometimes it makes sense to rename them, sometimes it is so engrained in daily life nobody would use the new names.
Can I rephrase the question to, what is the longest electromagnetic wavelength ever recorded?
Whales could understand it
