My partner and I are casually chatting about how strange the electromagnetic spectrum is, as we sometimes do. The idea came up of creating an antenna that vibrates at the right frequency to produce various colors of light. But then I remembered that “light is both a wave and a particle” … so can someone how photons (right?) relate to the rest of the electromagnetic spectrum?
In: 4
Photons are the entire electromagnetic spectrum. All light is photons.
Light behaves both like a wave and like a particle. When it’s behaving like a particle, that particle is called a photon.
Different colors of light are photons with different energy levels.
Yes photons of visible light are [part of the EM spectrum](https://gamma-sci.com/wp-content/uploads/2021/07/7.2.21-Electromagnetic-Spectrum.jpg). Visible light has a wavelength that’s shorter than infrared and radio, but longer than ultraviolet and x-rays. But it’s all just electromagnetic waves of different frequencies.
A good way to ELI5 the idea of a “photon” is to think of it as a “[wave packet](https://upload.wikimedia.org/wikipedia/commons/9/93/Wave_packet.gif)” – it’s still made of electromagnetic waves (aka ripples in the electric and magnetic fields), but each photon is like a little [bunch of ripples that moves along in a packet](https://upload.wikimedia.org/wikipedia/commons/b/b0/Wave_packet_%28dispersion%29.gif?20160130184257) that *together* has some particle-like properties as well as its wave-like properties.
All electromagnetic radiation – light, radio, X-Rays, gamma rays and so on – is made of photons. They all act like particles and like waves.
The ways they all act like waves include:
* they refract, they have interference patterns, they have a frequency and a wavelength
The ways they act like particles:
* they carry their energy in discrete chunks.
The higher the frequency, the more energy there is per chunk. And so, higher-energy EM radiation acts “more” like particles. Also, even normal waves tend to act less “wavy” at high frequencies / low wavelengths: For example, there’s a grille on the door of your microwave oven that bounces the microwaves (with wavelengths about the size of finger) straight back in, but light (with wavelengths smaller than a cell) just goes through the holes in the grille as if they were particles.
For example, gamma rays have such a high frequency that they almost always act like discrete particles. When there’s a nuclear reaction that emits gamma rays, it emits a single gamma ray with known energy and frequency. When an electron and a positron collide, they (almost always) give off exactly two gamma rays, each one the same energy.
Visible light photons contain much less energy each, so you need millions more to carry the same energy as a single gamma ray photon. So visible light acts a lot less like particles than gamma rays do. Still, we see them acting like particles when they hit solar panels to generate electricity, or when we switch on a fluorescent light, or wear glow-in-the-dark shoes.
Radio wave photons contain so little energy that even the faintest radio signal will be generating zillions of them. It requires very sensitive equipment to see the particle nature of radio waves, but it can be done.
NB: here’s some things that might seem mind-blowing:
* even a single photon still acts like a wave. For example, you can fire photons one at a time through a grille, and measure where they each, individually land – and the overall pattern of where they land will look just like you’d expect from a wave.
* even things we think of a “particles” (eg, electrons, protons, atoms, and people and planets) act like waves! But the bigger something is, the smaller its wavelength, and large objects would have such tiny wavelengths that the wave properties look exactly like particle motion.
Cool idea.But in the real workd, the vibrational frequency is so high that it would disintegrate any macroscale material object.
So The real world uses tiny things like electrons, instead. Check out how neon lights work, for a (relatively) simple example.
An antenna doesn’t vibrate – at least that’s not the mechanism by which it operates. An antenna is ultimately just a conductor through which a current is passed. Every conductor has an electric field around it and pulsing currents through it creates electromagnetic waves. The opposite also holds: electromagnetic waves around a conductor induce an electric current in that conductor. The length of the conductor determines the range of frequencies that the antenna can effectively transmit or receive.
The antenna may vibrate very slightly as a result of of the changing electromagnetic field, but that is just a side effect. Physically vibrating an antenna does not make it emit electromagnetic waves, nor does an antenna receive electromagnetic waves by measuring physical vibrations.
I think you may be conflating light/electromagnetic waves with sound, which *is* mediated by physical vibrations.
Photons aren’t *part* of the electromagnetic spectrum, they are the force carrier particle for *all* electromagnetic energy. Radio waves, gamma rays, x-rays, visible light…etc are all electromagnetic energy and thus, from a particle standpoint, are all just photons of different energies.
Latest Answers