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Visible light is simply part of the EM spectrum at certain wavelengths. I assume UV and infrared don't even qualify as "photons". So why do we have this concept of a photon when all it is, is a certain region of the EM spectrum? Are there Infrared particles? UV particles? Radio particles? What do they look like?

Is there a difference but wavelength?

I understand that EM waves can behave "as if they were particles", but that it seems just a crutch to understand quantum mechanics (double slit experiment and so on).

Opcode
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Isn't it just EM waves at a certain wavelength?

No. Photons have nothing to do with a particular range of wavelengths. A photon can have any wavelength. There are visible photons, infrared photons, ultraviolet photons, radio photons, X-ray photons, gamma ray photons, etc.

Asking what photons with non-visible wavelengths “look like” is not a meaningful question. Your eyes cannot see them, so they do not look like anything. However, your skin can feel the warmth of infrared photons.

On this site there is an expectation that you ask only one question at a time. I have focused on the one for which you have a misconception. You seem to already understand that light does not behave purely as a wave.

G. Smith
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I understand that EM waves can behave "as if they were particles", but that it seems just a crutch to understand quantum mechanics (double slit experiment and so on).

One can equally argue the other way that photons (particles) can collectively behave “as if they were particles.”

This is a common consequence of them, like all things in quantum mechanics, fundamentally being vectors in Hilbert space.

In physics, an encompassing theory trumps multiple disjoint theories.

Superfast Jellyfish
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Photons may be imagined as an imaginary point which represents an elementary portion of a wave with an up and a down. Photons should not be imagined as a particle. We need this imagination just to imagine a light wave as a ray. I ask the questioner to assume the followings (for which a basic theory may be found in a book entitled “Planets and electromagnetic waves”). The followings are based on mathematical interpretations for solutions of Maxwell equations. (1) If current exceeds some limit (depending on source of production), then magnetic field waves are produced. These waves are called in general radio waves. (2) If voltage exceeds some limit (depending on source of production), then electric field waves are produced. These waves are called in general light waves. (3) If current exceeds the corresponding limit and the voltage also exceeds the corresponding limit then both magnetic field waves and electric field waves exist separately; not in combined form (that is, not as everyone gives a figure for em waves with two component waves). A peculiar situation for (3) is the Hertz’s experiment. Both light waves (rays) and radio waves may be imagined in the same way for understanding purpose. Light rays are electric field waves. Radio waves are magnetic field waves. Wavelengths of light rays are less than or equal to 1.06 mm (approximately), and wavelengths of radio waves are greater than or equal to 1.06 mm. So, the guess given in the question is correct.

ganesa moorthy
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