Are there physical limits to the size of the electromagnetic spectrum? A Youtube video likens the visible spectrum to one frame of film in a 2000 mile length. This got me thinking about how the two extremes ends were determined. Doesn’t it extend into infinity?
I guess the plank length would be the shortest wavelength, or possibly the wavelength which gives a photon enough energy to form a black hole instantly. No maximum wavelength, as the light emitted by something falling into a black hole gets infinitely redshifted.
The first one sets the limit at 12.29 GJ of energy per photon, or a frequency of 1.85 x 10^43 Hz.
Is that really possible, given that a photon’s energy depends on the frame of reference?
That claim is broken in multiple ways. The most basic is: what mapping are they using to convert the spectrum to this notional film strip? One possible mapping would be a linear one, such that a given wavelength is marked on the strip a distance from the end that is proportional to the wavelength. In that case, if the visible spectrum is one film frame in length, then that frame itself must be located right at one end of the long strip, about 1.3 film frames in from the end. It certainly wouldn’t be lost amongst miles and miles of strip, as the claim perhaps implies.
If it’s a logarithmic scale, then the strip does extend in both directions, but the logarithm makes it very difficult to get far. Even taking arbitrary values for the large end (diameter of the observable universe) and the small end (Planck length), the logarithmic distance between those ends is only 250 times larger than the logarithmic distance between the two ends of the visible spectrum. That is, one film frame for the visible spectrum would correspond to only 250 frames for the entire large (but arbitrary) span chosen here.
As for the physics, there is no known hard cutoff in either (logarithmic) direction. A lone photon won’t spontaneously form a black hole (with scr4’s point being one way to demonstrate that), and nothing special is known to happen at the Planck length. That’s not to say there isn’t a lower limit in wavelength, but if there is one, we don’t know about it yet.
Yes and no (at the same time)
But since this is a oscillation, a frame of reference does not negate the conjecture, but it is interesting when a specific frame of reference allows it and another does not.
No and no, and not yes. There are many things that depend on frame of reference, some of them quite surprising, but whether something is a black hole is not one of them. There is no indication from any currently-known theory of physics that it would be possible for a single photon to turn into a black hole, nor any indication of any other problem with a photon with arbitrarily-large energy.
Hope you don’t mind a slight hijack, to whit: is it possible to design an elecctro magnetic lens for the visible spectrum rather than an optical glass lens.
Peter
I don’t know what an electromagnetic lens is, but I’ve always wondered if it might be possible to design a transmitter so that instead of broadcasting radio or tv waves, it might broadcast green or orange instead.
Wouldn’t that be a specific-wavelength LED? Or a colored lightbulb?
Visible light is just that part of the Electro Magnetic Spectrum that Humans can see.
No reason, and I fully expect to be shot down in flames, that we can’t design a device apart from optical, ie glass, to focus those those frequencies.
No?
Peter
If you mean focusing light using just electromagnetic fields, no, because photons don’t have a charge. You can, however, focus electrons using electromagnetic fields, and this is done in electron microscopes.
In a sense, optical glass is an EM lens. Photons interact with electrons, and the glass has the electrons in the right places, with the right properties, to usefully interact with your light.
You can make lots of materials that have the right properties, from a whole range of elements. Funny thing is that when you do, we have a habit of calling them optical materials. (They don’t need to be a glass. Plastics for instance are typically not glasses, nor are crystals)
You can make lenses for any EM energy with a wavelength longer than ultraviolet. Some wavelengths are difficult - it is hard to find materials they will pass through. But when you get down to radio-waves you just use lengths of conductive material to interact with the EM field. Appropriate choice of lengths and geometry and you can focus the energy. Some the so called meta-materials in the press recently that make an object invisible to radar do this.
But as Chronos points out. An EM field will not interact with photons. It is essentially like trying to use photons to bend another beam of photons. Photons don’t do this. You need the other half of the pair - [photons, particles with charge], to interact with photons. Electrons are the easiest.
Actually, the scattering of light by electromagnetic fields has been observed (see the Delbruck Effect, named after Max, not Hans), although the sought0-after scattering of light bb y light has apparently not been observed yet:
And this is simply scattering, not directed, purposeful focusing of light. Even so, it’s a fleetingly small effect. I wouldn’t put my hopes on any sort of real EM-only lens. as I’ve mentioned before, electro-optical effects invariably rely on affecting the medium through which the photons propagate (or are absorbed or generated), rather than affecting the photons themselves