<p>Angular resolution, e.g. from this Q&amp;A from Physics Stack Exchange:</p>
<p><a href="https://physics.stackexchange.com/questions/606056/what-is-the-pixel-resolution-of-a-human-eye">https://physics.stackexchange.com/questions/606056/what-is-the-pixel-resolution-of-a-human-eye</a></p>
<p>is indeed going to give you the limit of what can be resolved for light projected into the eye. That gives a resolution around 1 arcminute; from <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC6660219/" rel="nofollow noreferrer">https://pmc.ncbi.nlm.nih.gov/articles/PMC6660219/</a> it seems there's about 1 cone per 3 square arcminutes. So, that angular resolution is pretty much matching the density of cones, which makes sense: there's no more information possible to come from the outside world, so no benefit to having cones at any higher density.</p>
<p>If you only stimulate a single photoreceptor, the most you would be able to perceive is a spot of light, or a flash if it's brief. You need to stimulate multiple photoreceptors in some pattern if you want to see a pattern. It doesn't matter what the shape of the original &quot;molecule&quot; or whatever you are imagining the light coming from. Think about a bitmap image with just one pixel colored:</p>
<p><a href="https://i.sstatic.net/lQbCMkk9.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/lQbCMkk9.png" alt="Black image with a single white pixel" /></a></p>
<p>That's the only information the retina has in the scenario you describe, so that's all there is to possibly perceive.</p>

CC BY-SA 4.0
2024-11-07T22:47:39.193Z
2024-11-07T22:47:39.193Z
Bryan Krause
<p>I only studied science till my high school but there is this one question I always wandered about is that Can we see very tiny objects like molecules in isolation(i.e let's say a single molecule and there is nothing around it so it can't blend in the surrounding light)? Because if our photoreceptors can sense even a single photon than it will stimulate atleast one of our photoreceptor at a time so we should be able to detect it? Most people give the argument of <strong>&quot;angular resolution&quot;</strong> to counter this, but I don't think it applies here because its the limit after which the image of two points merges onto a single point on retina and we can't distinguish very tiny objects from its background but here ,there is <strong>NO background signal and only one small object like a molecule is there so only one photoreceptor is recieving the signal</strong>.And if let's say  intensity does matter for us then what if the molecule is bright enough &quot;hypothetically&quot; (by bright I mean it is able to shoot a lot of photons onto just one photoreceptor of the retina) and it stimulate just one photoreceptor continuously, then would we able to detect it? If yes, how our brain would detect it's edges i.e how would we know its shape? And if we can't recognise something's edges then how can we form it's image?</p>
<p><strong>To  sum up my question is &quot;What would our brain do if ONLY one photoreceptor is stimulated(and this is possible by objects which are smaller than even a single photoreceptor cell), would it recognise the presence of something and generate a visual response? If yes, how would it determine its shape?</strong> because as far as I think one photoreceptor wouldn't be able to do it because I think a lot of photoreceptors are required for this. But I don't know for sure ,I might be wrong.</p>

CC BY-SA 4.0
2024-11-07T12:44:49.380Z
Welcome. Do you mean to ask whether we can see a single photon or what happens when a single photoreceptor is flooded with photons? The latter is difficult to test and I don't know of the existence of any such studies (I cannot think of a feasible setup), the former question is answerable
AliceD
CC BY-SA 4.0
2024-11-07T12:47:21.770Z
...and secondly - you ask about recognizing a shape with a single photorecepor; technically you could follow a shape's outline with your gaze and mentally shape an image; can you clarify your question on both these issues?
AliceD
CC BY-SA 4.0
2024-11-07T16:06:42.840Z
@AliceD this question came to my mind when I was thinking "WHY can't we actually see very tiny objects like atoms/molecules". I got a lot of explanation which are -1) because they are tiny( I mean yeah I know it's tiny but it doesn't answer the fundamental question "why" so it's not really useful if we wanna set the limit of what "tiny" actually is) 2)some people argued "angular resolution as the reason(okay I accept it that all these molecules are so packed that they blend among each other) 3)A lot of people said "light from that is not INTENSE enough"
Virender Bhardwaj
CC BY-SA 4.0
2024-11-07T16:08:46.577Z
@AliceD considering all of this in mind . This question arose in my mind that "what if something as tiny as a single atom is COMPLETELY isolated and intense enough that is shooting enough photons on our retina in visible range. Would we be able to detect it then? And as it's so tiny. It will be able to stimulate just One photoreceptor at a time. That's why I asked what will happen in this case where just one photoreceptor is stimulated
Virender Bhardwaj
CC BY-SA 4.0
2024-11-07T16:14:52.490Z
@AliceD and the thing about "shape" what I mean is. Suppose if something is as tiny as a molecule but is hexagonal in shape(present in all other conditions I mentioned above).That would definitely stimulate just one photoreceptor at a time as it's too tiny. And on the other hand something which is of some different shape would do the same thing. So would our brain be able to detect it's shape? If yes how? Both signals are completely the same. If not, then what image would our brain form?
Virender Bhardwaj
CC BY-SA 4.0
2024-11-07T16:18:40.393Z
So, judging from the comments, your question is about the physics of light. Why would you post on a psychology site (and a biology one)? The width of an atom. The wavelength of light. Please look-up those two things to get an idea of the basics of the scale of objects you're trying to see. (I.e. compare a sharp pencil with a wide paintbrush - which is better for signing your name on a document?)
Jiminy Cricket.
CC BY-SA 4.0
2024-11-07T17:11:29.743Z
@JiminyCricket. I had already asked it on physics.stackexchange and the responses I wrote it in the comments is all what I got from there. But now seeing all of them this question of just stimulation of one photoreceptor arises which I think is more of a biology question.
Virender Bhardwaj
CC BY-SA 4.0
2024-11-07T17:19:18.987Z
The link I gave you on the biology site was to a question which answered the question regarding the sensitivity of photoreceptors. The question here as written seems to contain the roots of several questions: the physics of electromagnetic/matter interactions, the sensitivity of photoreceptors and the modeling of shapes in the brain. Please separate out all the elements and just ask about the relevant ones on each site. Asking about photons/molecules and photon-interactions is not suited to a psychology site. Please edit the question to focus it to what we can do here.
Jiminy Cricket.
<neuroscience><vision><neurophysiology><neuroimaging><visual-memory>
What would our brain perceive if ONLY one photoreceptor is stimulated?
Virender Bhardwaj
# What would our brain perceive if ONLY one photoreceptor is stimulated?

(Asked by: username_0 on 2024-11-07)

I only studied science till my high school but there is this one question I always wandered about is that Can we see very tiny objects like molecules in isolation(i.e let's say a single molecule and there is nothing around it so it can't blend in the surrounding light)? Because if our photoreceptors can sense even a single photon than it will stimulate atleast one of our photoreceptor at a time so we should be able to detect it? Most people give the argument of **"angular resolution"** to counter this, but I don't think it applies here because its the limit after which the image of two points merges onto a single point on retina and we can't distinguish very tiny objects from its background but here ,there is **NO background signal and only one small object like a molecule is there so only one photoreceptor is recieving the signal**.And if let's say intensity does matter for us then what if the molecule is bright enough "hypothetically" (by bright I mean it is able to shoot a lot of photons onto just one photoreceptor of the retina) and it stimulate just one photoreceptor continuously, then would we able to detect it? If yes, how our brain would detect it's edges i.e how would we know its shape? And if we can't recognise something's edges then how can we form it's image?

**To sum up my question is "What would our brain do if ONLY one photoreceptor is stimulated(and this is possible by objects which are smaller than even a single photoreceptor cell), would it recognise the presence of something and generate a visual response? If yes, how would it determine its shape?** because as far as I think one photoreceptor wouldn't be able to do it because I think a lot of photoreceptors are required for this. But I don't know for sure ,I might be wrong.

**Tags:** neuroscience, vision, neurophysiology, neuroimaging, visual-memory

> **Comments:**
> **username_1**: Welcome. Do you mean to ask whether we can see a single photon or what happens when a single photoreceptor is flooded with photons? The latter is difficult to test and I don't know of the existence of any such studies (I cannot think of a feasible setup), the former question is answerable  
> **username_1**: ...and secondly - you ask about recognizing a shape with a single photorecepor; technically you could follow a shape's outline with your gaze and mentally shape an image; can you clarify your question on both these issues?  
> **username_0**: @username_1 this question came to my mind when I was thinking "WHY can't we actually see very tiny objects like atoms/molecules". I got a lot of explanation which are -1) because they are tiny( I mean yeah I know it's tiny but it doesn't answer the fundamental question "why" so it's not really useful if we wanna set the limit of what "tiny" actually is) 2)some people argued "angular resolution as the reason(okay I accept it that all these molecules are so packed that they blend among each other) 3)A lot of people said "light from that is not INTENSE enough"  
> **username_0**: @username_1 considering all of this in mind . This question arose in my mind that "what if something as tiny as a single atom is COMPLETELY isolated and intense enough that is shooting enough photons on our retina in visible range. Would we be able to detect it then? And as it's so tiny. It will be able to stimulate just One photoreceptor at a time. That's why I asked what will happen in this case where just one photoreceptor is stimulated  
> **username_0**: @username_1 and the thing about "shape" what I mean is. Suppose if something is as tiny as a molecule but is hexagonal in shape(present in all other conditions I mentioned above).That would definitely stimulate just one photoreceptor at a time as it's too tiny. And on the other hand something which is of some different shape would do the same thing. So would our brain be able to detect it's shape? If yes how? Both signals are completely the same. If not, then what image would our brain form?  
> **username_2**: So, judging from the comments, your question is about the physics of light. Why would you post on a psychology site (and a biology one)? The width of an atom. The wavelength of light. Please look-up those two things to get an idea of the basics of the scale of objects you're trying to see. (I.e. compare a sharp pencil with a wide paintbrush - which is better for signing your name on a document?)  
> **username_0**: @JiminyCricket. I had already asked it on physics.stackexchange and the responses I wrote it in the comments is all what I got from there. But now seeing all of them this question of just stimulation of one photoreceptor arises which I think is more of a biology question.  
> **username_2**: The link I gave you on the biology site was to a question which answered the question regarding the sensitivity of photoreceptors. The question here as written seems to contain the roots of several questions: the physics of electromagnetic/matter interactions, the sensitivity of photoreceptors and the modeling of shapes in the brain. Please separate out all the elements and just ask about the relevant ones on each site. Asking about photons/molecules and photon-interactions is not suited to a psychology site. Please edit the question to focus it to what we can do here.  

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## 1 answers

### Answer by username_3 on 2024-11-07. Score: 1

Angular resolution, e.g. from this Q&A from Physics Stack Exchange:

<https://physics.stackexchange.com/questions/606056/what-is-the-pixel-resolution-of-a-human-eye>

is indeed going to give you the limit of what can be resolved for light projected into the eye. That gives a resolution around 1 arcminute; from <https://pmc.ncbi.nlm.nih.gov/articles/PMC6660219/> it seems there's about 1 cone per 3 square arcminutes. So, that angular resolution is pretty much matching the density of cones, which makes sense: there's no more information possible to come from the outside world, so no benefit to having cones at any higher density.

If you only stimulate a single photoreceptor, the most you would be able to perceive is a spot of light, or a flash if it's brief. You need to stimulate multiple photoreceptors in some pattern if you want to see a pattern. It doesn't matter what the shape of the original "molecule" or whatever you are imagining the light coming from. Think about a bitmap image with just one pixel colored:

[![Black image with a single white pixel](https://i.sstatic.net/lQbCMkk9.png)](https://i.sstatic.net/lQbCMkk9.png)

That's the only information the retina has in the scenario you describe, so that's all there is to possibly perceive.


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