The Theory of Light and the Theory of Vision

This is not an everything goes forum, but rather a place to ask questions and request help for developing your ideas.

The Theory of Light and the Theory of Vision

Postby Odal on October 18th, 2017, 6:33 am 

The Theory of Light and the Theory of Vision

Both Physics and Psychology - some prefer Cognitive Science- take Optics as the fundament on which further theoretical developments are based.
A central tenet of Optics is that we see objects because photons impinge on our retina, creating retinal images which are then translated by our brain into perceptions.

The aim of this thread is neither to disprove nor to defend but to understand.

My question concerns this very fact of vision.

When a (laser) beam is directed away from us, let us say, horizontally relative to where we are standing, we are still able to see it.

We are also able to see an illuminated object even if we are standing in complete darkness.

The (informal) response I got until now is that photons still reach our eyes in such conditions, creating the visual sensations.

My understanding of light theory in general, and the Huygens Principle in particular, is that everything in a wave is centered around the forward direction. Side phenomena, wavelets, are limited to a minimum to keep the wave going forward.

Also, electric and magnetic field have a limited range, and contribute principally, if not solely, to the forward movement.

My question then is: how can photons be created that propagate in all directions, making it possible for us to see a beam of light even if it is not directed toward us?

I understand the effect that e.m waves have on particles of matter, and that that could explain how light reflected of these particles would be propagated in all directions. But I wonder if the explanation is in itself sufficient.
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: The Theory of Light and the Theory of Vision

Postby Braininvat on October 18th, 2017, 10:17 am 

We see a laser beam from the side because of particulates in the air that scatter some of the photons. Even the air molecules play a role in scattering photons. Some bounce in our direction. In the vacuum of space, we do not see a laser beam from the side.
User avatar
Braininvat
Forum Administrator
 
Posts: 6875
Joined: 21 Jan 2014
Location: Black Hills
Faradave liked this post


Re: The Theory of Light and the Theory of Vision

Postby Odal on October 18th, 2017, 10:21 am 

Do photons then reach us everywhere where we stand? How is it compatible with the Huygens Principle? Isn't the energy of the beam then being spread all over space, instead of being concentrated in the forward direction?
Also, how come we can stand in total darkness and still see objects distant from us?
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: The Theory of Light and the Theory of Vision

Postby curiosity on October 18th, 2017, 1:05 pm 

As Biv has said, you can see a laser beam from a side view mainly because of what is known as Rayleigh scatter, caused by gas molecules in our atmosphere. You may want to google it for a fuller explanation.
curiosity
Member
 
Posts: 386
Joined: 19 Jul 2012


Re: The Theory of Light and the Theory of Vision

Postby Odal on October 18th, 2017, 1:07 pm 

curiosity » October 18th, 2017, 6:05 pm wrote:As Biv has said, you can see a laser beam from a side view mainly because of what is known as Rayleigh scatter, caused by gas molecules in our atmosphere. You may want to google it for a fuller explanation.


I know about the scattering, I was just wondering how far it went in all directions. And what happened when we stand in total darkness.
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: The Theory of Light and the Theory of Vision

Postby Odal on October 18th, 2017, 4:27 pm 

If you shine a (laser) beam through a water tank, the water having been made somewhat murky, you will see the Raleigh scattering. But it will stop more or less abruptly and only the (larger) beam will be visible.
Light looses its intensity with distance, until it disappears completely. Still, we can see it from very far away.

How is that possible?
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: Singles that Mingle

Postby Faradave on October 18th, 2017, 7:23 pm 

You might wish to consider a single-photon light source. This is typically a very low intensity laser, where some of the photons are intentionally reflected out of the beam. They're not perfect but provide single photons with a good degree of certainty (80-90% of the time).

Assuming a single photon, on a trajectory toward a suitable absorber, it can either make it or it can have its trajectory altered by an intervening material which absorbs or scatters it. As far as the detector (which may be your eye) is concerned, the photon either makes it or not. The amount of intervening distance is generally irrelevant except for the expected travel time.

Light is best considered photonic only when interacting directly with particles (e.g. emitter, absorber, scatterer). In transit, the wave characteristics predominate. You can never "see" a single photon from the side in transit because there's nothing to see. But you can influence its wave aspect, as with double-slit interferometry.
User avatar
Faradave
Active Member
 
Posts: 1765
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: Singles that Mingle

Postby Odal on October 18th, 2017, 7:28 pm 

Faradave » October 19th, 2017, 12:23 am wrote:You might wish to consider a single-photon light source. This is typically a very low intensity laser, where some of the photons are intentionally reflected out of the beam. They're not perfect but provide single photons with a good degree of certainty (80-90% of the time).

Assuming a single photon, on a trajectory toward a suitable absorber, it can either make it or it can have its trajectory altered by an intervening material which absorbs or scatters it. As far as the detector (which may be your eye) is concerned, the photon either makes it or not. The amount of intervening distance is generally irrelevant except for the expected travel time.

Light is best considered photonic only when interacting directly with particles (e.g. emitter, absorber, scatterer). In transit, the wave characteristics predominate. You can never "see" a single photon from the side in transit because there's nothing to see. But you can influence its wave aspect, as with double-slit interferometry.


Is that a reply to my posts or to another discussion: Single that mingles?
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: Entitlements

Postby Faradave on October 19th, 2017, 10:20 am 

Hi Odal,

As there is little point in every post having the same title, the edit window permits individual post titling. By default, this is filled in with the thread title, for those who just want to focus on the body of the reply. My titles tend toward the ridiculous. Sorry for the confusion.

So yes, that post was for you. A light quantum is not generally detectable as a particle while in transit, though its spread-out wave aspects can be influenced. Wave-particle duality is a longstanding mystery in physics.

P.S. Underlined text (usually having blue text or underline) typically indicates an active reference link. Click to follow these.
Last edited by Faradave on October 19th, 2017, 10:23 am, edited 1 time in total.
User avatar
Faradave
Active Member
 
Posts: 1765
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: Entitlements

Postby Odal on October 19th, 2017, 10:23 am 

Faradave » October 19th, 2017, 3:20 pm wrote:Hi Odal,

As there is little point in every post having the same title, the edit window permits individual post titling. By default, this is filled in with the thread title, for those who just want to focus on the body of the reply. My titles tend toward the ridiculous. Sorry for the confusion.

So yes, that post was for you. A light quantum is not generally detectable as a particle while in transit, though its spread-out wave aspects can be influenced. Wave-particle duality is a longstanding mystery in physics.

P.S. Underlined text (usually having blue text or underline) typically indicates an active reference link. Click to follow these.



Then I am afraid I do not understand the relevance of your comment. I am quite familiar with the double slit experiment and affiliated issues, so please be more explicit in your meaning.
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: Field of Vision

Postby Faradave on October 19th, 2017, 10:32 am 

Odal wrote:Light looses its intensity with distance, until it disappears completely. Still, we can see it from very far away.

The wave aspect of light looses intensity as a field, falling off with radius squared from the source. An individual photon does not change it's energy at all (ignoring gravity and relative motion of emitter & absorber.) Your eye will see a photon undiminished, regardless of distance.
User avatar
Faradave
Active Member
 
Posts: 1765
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: Field of Vision

Postby Odal on October 19th, 2017, 10:39 am 

Faradave » October 19th, 2017, 3:32 pm wrote:
Odal wrote:Light looses its intensity with distance, until it disappears completely. Still, we can see it from very far away.

The wave aspect of light looses intensity as a field, falling off with radius squared from the source. An individual photon does not change it's energy at all (ignoring gravity and relative motion of emitter & absorber.) Your eye will see a photon undiminished, regardless of distance.


That is exactly the problem I am trying to solve, and I am afraid I need more that a simple affirmation.
Is what make objects visible, and luminous, the same as what make me see these objects?
It seems to me that the term photon is used in so many meanings and configurations as to lose any meaning.

Light falls on an object, and makes it luminous.
The same light, reflected by this object makes me see this luminous object.

But while the first light makes everything luminous, also in the form of ambient light, the light that reaches my eyes apparently only affects my eyes, and not anything else.

That is what I find difficult to understand.
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: Scatterbrained

Postby Faradave on October 19th, 2017, 10:54 am 

Odal wrote:But while the first light makes everything luminous, also in the form of ambient light, the light that reaches my eyes apparently only affects my eyes, and not anything else.

This is why replies mention "scattering". Sunlight hitting the moon is comprised by uncountably large numbers of photons. As the moon's surface is irregular, they reflect off in all directions (i.e. they scatter). Those particular photons seen by your eye are not seen by anyone else. Other people see different photons.

If the moon is illuminated by just a single photon, then at most, one person will see that reflected photon (in fact, with just one eye). The moon would be dark to everyone else (ignoring the moon's black body radiation).

P.S. My posts continue to edit for several minutes after I first post them, usually for minor adjustments.
User avatar
Faradave
Active Member
 
Posts: 1765
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: The Theory of Light and the Theory of Vision

Postby Odal on October 19th, 2017, 11:28 am 

I have to concede that I cannot win a rational discussion of light theory.

What would falsify this theory, in all its aspects, or each aspect apart?
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: Broken in Two

Postby Faradave on October 19th, 2017, 11:58 am 

As Einstein wrote:

"It seems as though we must use sometimes the one theory and sometimes the other, while at times we may use either. We are faced with a new kind of difficulty. We have two contradictory pictures of reality; separately neither of them fully explains the phenomena of light, but together they do."

Physics has gotten quite used to this conflict and recognizes the need for a better model. QED is a famous and very successful attempt but relies heavily on "virtual photons", which to my mind perpetuate the conceptual problem.

I deny photons altogether in my own personal theory but would not further burden this thread.
User avatar
Faradave
Active Member
 
Posts: 1765
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: Broken in Two

Postby Odal on October 19th, 2017, 12:01 pm 

Faradave » October 19th, 2017, 4:58 pm wrote:As Einstein wrote:


I deny photons altogether in my own personal theory ...

which thread is it?
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)


Re: Manning the Out Post

Postby Faradave on October 20th, 2017, 1:48 am 

Odal wrote:which thread is it?


I don't recommend that, unless you're fairly familiar with Special Relativity (i.e. Minkowski spacetime, intervals, invariance, etc.). This post (skip the videos) gives a brief summary.
User avatar
Faradave
Active Member
 
Posts: 1765
Joined: 10 Oct 2012
Location: Times Square (T2)


Re: Manning the Out Post

Postby Odal on October 20th, 2017, 6:36 am 

Faradave » October 20th, 2017, 6:48 am wrote:
Odal wrote:which thread is it?


I don't recommend that, unless you're fairly familiar with Special Relativity (i.e. Minkowski spacetime, intervals, invariance, etc.). This post (skip the videos) gives a brief summary.


I certainly do not master the math, but I am confident I understand the metaphysical assumptions and consequences.
Odal
Banned User
 
Posts: 62
Joined: 17 Oct 2017
Blog: View Blog (1)



Return to Personal Theories

Who is online

Users browsing this forum: No registered users and 11 guests