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Naive_Age_566 t1_j4744sx wrote

a photon detector IS a photon absorber

the photons are absorbed by the cells in your retina. basically, the energy of those photons excite some atoms. that excitation generates some electrical current. that current prompts some neurons to send an electro-chemical signal to your brain.

and yes - the photons are "destoryed" in that process (aka: it's energy is converted into another form of energy)

a photon is not some kind of miniature cannonball. it is kind of a packet of energy, that is transmitted in a wave over the electromagnetic field. take away the energy and the wave "goes flat".

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deviantbono t1_j47fcyk wrote

IIRC, when the energy in the photon is absorbed by the physical "detector", the "detector" changes shape, altering its output, but does NOT actually "send" a signal to the brain as a result, it actually STOPS sending a signal. That non-signal is then what is interpreted as visual meaning.

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CrateDane t1_j48indt wrote

The detector itself is technically part of the brain, as is all of the retina. It's true that the response of the cells that detect light is the opposite of normal neuron activation - hyperpolarization instead of depolarization. That gets swapped around before the signal leaves the retina though, along with some early processing taking place.

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AnattalDive t1_j47pfoz wrote

is that also the reason the speed doesnt matter? i wondered a few days ago how plants can absorb photons traveling at the speed of light

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Naive_Age_566 t1_j4a4up3 wrote

get the idea, that a photon is some kind of physical object, out of your mind. light is energy, that is transmitted over the electromagnetic field as a wave. but that wave can not take arbitrary values but only discreet multiples of a fixed value. kind of a packet of energy. and we call this packet of energy a photon. light is still an electromagnetic wave but it can only be produced and absorbed photon per photon.

there is this electromagnetic wave. and if this wave has the right wavelength (=energy density), it can excite a special molecule (the chlorophyll) in a special way that it can break the chemimal bonds between carbon dioxide molecules (co2) and water molecules (h2o) to form glucose molecules (c6h12o6) releasing some free oxygen in the process. (of course it is much more complicated than that). the chemical energy stored in glucose is higher than that of carbon dioxide or water. thats the reason, why the plant does this in the first place - glucose can be used to store energy. that energy must come from somewhere. and you guessed it: it is transformed from the light, the chlorophyll has absorbed.

the speed of the wave is irrelevant. one moment, there is no wave (just the "flat" electromagnetic field) and the chlorophyll is kind of in a dormant state. the next moment, there is a wave, consisting of - lets say, 10 packets of energy (10 photons). that energy is enough to excite the chlorophyll. it can catalyse carbon dioxide and water to glucose and free oxygen. the next moment, there is no wave anymore. aka: no more energy packets. the chlorophyll gets dormant again. photosynthesis stops.

it's not miniature balls zipping past at incredible speed! it's energy transmitted as waves. the speed of that wave is irrelevant. what matters is: is there NOW enough energy you can sap from the electromagnetic field to do something or not.

and to hammer down the obvious: if you turn on the light for 10 seconds in an otherwise dark room, there is kind of a wave front, that lasts for 10 seconds. in that 10 seconds, the electromagnetic field in direct vicinity around the chlorophyll molecule carries enough energy to do something. you only notice, that this wave arrived at the speed of light, if you compare the field strenghs of your own point with other points in the distance.

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Krail t1_j4a4ldm wrote

> The thing to understand about photons is that they are just little bits of electromagnetic energy.

This is a big thing to understand. Photons are essentially just little energy fluctuations. When they're absorbed, that means their energy is taken up by a charged particle (generally a proton or electron), and that energy is converted into another form of energy, which could be, for example, heat, electrical current, or chemical reactions.

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JoakimSpinglefarb t1_j4elty6 wrote

So what you're saying is that your eyes pick up good vibrations because they give them the excitations?

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Furrypocketpussy t1_j48op3x wrote

The back of your eye is packed with rods and cones (mostly rods, about 120 million of them vs 6m cones) and the photon is absorbed by them. Inside rods you have stacks of proteins called optic disks, that have rhodopsin in them, which has a small molecule called 11-cis retinal. When light comes through the pupil and hits the rod, some of it will hit the rhodopsin and cause a change in retinal to 11-trans retinal. This change in shape will cause a cascade that closes sodium channels on the rod and essentially turns the cell "off". The turning off of the rod will turn on a bipolar cell which then turns on a retinal ganglion cell that finally sends a signal via the optic nerve to the brain

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Sharlinator t1_j47oiis wrote

The inside of your eye is a "dark room" like the insides of a camera; your pupils appear black even though they are transparent because the retina is dark and reflects little light. Light bouncing around the eyeball would cause glare and reduction of contrast.

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[deleted] t1_j474g46 wrote

[removed]

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almightySapling t1_j4769qh wrote

Would the later emitted photon necessarily have a lower frequency? If the electron is moving between the same two shells it would be the same frequency, right?

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