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Why can't we see molecules with the naked eye?


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because they're too small funnily enough.

 

your eye has limited focusing ability and limited resolution. neither are good enough to view molecules straght on.

 

but its more than that. molecules are smaller than another physical limit on the performance of the eye. they are smaller than the photons with which you are trying to observe them with. basically the photons will just pass them by most of the time.

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but its more than that. molecules are smaller than another physical limit on the performance of the eye. they are smaller than the photons with which you are trying to observe them with. basically the photons will just pass them by most of the time.

 

But aren't photons supposed to be smaller than molecules? Aren't photons point-particles without a size?

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But aren't photons supposed to be smaller than molecules? Aren't photons point-particles without a size?

 

Resolution is not just to do with the photon size.

 

Giving the size is a bit unreal, they are not particles in a classical way. They do have some length associated with them though, their wavelength, which is important when considering resolution. And the absolute limit to resolution is the wavelength of light.

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well i guess say your retina has like a million cells so your eye's resolution is a million, whereas what you're looking at has like trillions of molecules. each of those retina cells is like one pixel, think about it.

 

except maybe i got the numbers wrong

Edited by dr432
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well i guess say your retina has like a million cells so your eye's resolution is a million, whereas what you're looking at has like trillions of molecules. each of those retina cells is like one pixel, think about it.

 

except maybe i got the numbers wrong

No you got the whole concept completely wrong as they aren't like pixels, firstly you have two eyes which vastly increases the resolution, also there are two different types of cells meaning it would change in different light levels as well as being based on how fast you are moving due to it not actually being a camera.

 

There seem to be lots of answer to the question on the web however none which I found seem to take into account the number of cells your eyes have which would seem a vitally import integer to have in the equation.

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There seem to be lots of answer to the question on the web however none which I found seem to take into account the number of cells your eyes have which would seem a vitally import integer to have in the equation.

 

The resolution limit of the optics dominates over the resolution limit of the "detector array", by this I mean that the size and space of the cells is small enough that doubling the number and density will not result in a resolution increase because there is not enough information in the light hitting them to matter.

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The actual cells, however, are much, much larger than an individual molecule.

 

Furthermore, the number alone doesn't tell you much for two reasons.

 

First, while in some cases even a single photon can trigger the photoreceptor, the nerve it relays information to will not be triggered by a single photoreceptor firing. So there's a real issue of sensitivity.

 

Second, and more importantly, the nerve immediately efferent (towards the brain, in the 'flow of information' sense) to the photoreceptor is actually integrating multiple adjacent photoreceptors, and will fire more strongly, for instance, if two photoreceptors it innervates fire differently (aiding in contrast).

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  • 1 year later...

well i guess say your retina has like a million cells so your eye's resolution is a million, whereas what you're looking at has like trillions of molecules. each of those retina cells is like one pixel, think about it.

 

But if color perception is only possible when light enters our retina, then why can we see colors who don't enter our eyes like in these cross-shaped stars?

 

ig278_amz_cone_nebula.jpg

Edited by Uri
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Here are some pictures of unusually large molecules. They were easy to see.

http://en.wikipedia.org/wiki/File:Cullinanroughpieces.jpg

 

In principle it's possible to see a single hydrogen atom, provided it is brightly lit and against a dark background. If it scatters enough visible photons towards your eye then you will see it.

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John Cuthber,

 

The problem with this theory is that in the picture I posted of the stars, you can see that the stars radiate in directions that are not directed toward our eyes but we can still see the color spectrum. Why is that?

 

These "crosses" in the image are a result of diffraction in the telescope optics, not us observing light that was heading in different directions.

 

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=0065MN

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But why are there different colors at all? Why is not everything the same color?

 

I guess that different colors exist in order for us to be able to differentiate between objects because color is the only way for us to differentiate between far-away objects without being able to touch them or hear the sound they make.

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But why are there different colors at all? Why is not everything the same color?

 

I guess that different colors exist in order for us to be able to differentiate between objects because color is the only way for us to differentiate between far-away objects without being able to touch them or hear the sound they make.

 

I'm not quite sure what you mean. Why would everything be the same color? Color is just the wavelength of light.

 

If you mean what is the use to us of being able to distinguish the wavelengths of light that enters our eyes, then yes, of course, it helps us perceive the world around us. You can still see without it, though. It's the difference between a color photograph and a black and white photograph. One just gives you more information.

 

Both are quite limited, though. Our eyes can only detect a very narrow range of wavelengths compared to all the light that exists. And our color perception even within that range is easily fooled - we can't distinguish between yellow light and a mixture of red and green light, which is why computer displays and televisions can show us all colors using only different mixtures of red, green, and blue light.

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If I look up and see a distant star it may no longer exist. It might have died before there were any people to see what colour it was so, whatever the reason for the colour, it certainly can't be for our benefit.

This "I guess that different colors exist in order for us to be able to differentiate between objects" doesn't make sense.

Some stars are redder because they are cooler.

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