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When with an incident ray a photon of sufficient energy meets an electron it can eject it from matter. But outside of matter, we still have the probability that other photons meet this electron and orient its course in the direction of the radiation. Has this been observed? If yes or no, what is the explanation? Malypaet (talk) 09:20, 9 September 2024 (UTC)[reply]
Compton scattering, the effect of the interaction of a photon and a charged particle, usually an electron, also applies to the interaction of photons and solitary electrons. If no energy is needed to release bound electrons, this form of scattering already occurs with low-energy photons and is then known as Thomson scattering. --Lambiam13:06, 9 September 2024 (UTC)[reply]
I read these articles, but what is missing is the notion of time. A radiation is a flow of energy (a rate), so an electron in a volume crossed by a radiation will experience a force in the direction of the radiation, as long as it is in this volume, ok. As it accelerates, it releases energy in the form of radiation (synchrotron effect?), so it loses acceleration. I suppose that the trajectory of the electron is a curve that brings it in the direction of the incident radiation? Do we know the equation of this curve? Malypaet (talk) 21:14, 9 September 2024 (UTC)[reply]
Acceleration is a change in velocity. In the scenario of a photon interacting with a free electron, the only change in velocity is at the moment of interaction. Before and after, in the absence of external forces, their velocities are constant. --Lambiam22:45, 9 September 2024 (UTC)[reply]
But in radiation that is a photon flow, there are more than one photon, so the probability that other photons successively (in time) hit the electron is not null. Then, in this term of probability, you can have a trajectory and a curve with a point in space and time for each interaction, isn't it? Malypaet (talk) 08:35, 10 September 2024 (UTC)[reply]
I've just been trying to think. There are lots that are black/brown/white and I can think of several yellow, green, blue and red vertebrate animals (mostly birds), but very few that are predominantly purple. Is this the rarest colour in nature? Iloveparrots (talk) 21:44, 9 September 2024 (UTC)[reply]
left: azzurro; right: blu One problem in addressing the question is that colour names cover a fuzzy region in a multi-dimensional space of colours. The 23 examples of purple vertebrates shown here display a wide range of purplish colours. For a reasonable comparison between named colours, the regions need to have similar sizes. The region we call "blue" is split in Italian into two regions considered to have different colours: azzurro and blu. --Lambiam23:24, 9 September 2024 (UTC)[reply]
Peripheral to this question is a semi-ontological question of what it means to "be" a certain colour. Many colour are difficult or impossible for organisms to replicate via pigment, and so the impression of the colour is instead created through layered tissues or structures that diffuse reflected light of varying wavelengths deferentially. SnowRise let's rap00:43, 22 September 2024 (UTC)[reply]
