Does light ever go from the eye to the image?

[lioric]

TL;DR

The kid wrote that the direction of the light should be coming to the eye from the image. But the teacher marked it wrong and said that the light would come from the eye to the image

You can see from the picture that the teacher has circled the arrows which shows light coming from image to the eye, and drew it in the opposite direction saying the light goes from the eye to the image.
The marking scheme of this paper only says the correct direction does not specify which is the correct direction. But on YouTube there is a video of a person doing this question and he draws the arrows this way

here is the link to the video with the timecode


but I have not found any other sources on the web showing that light travels from eyes to the image. And it makes no sense to me.

so I turn to you guys.
please give me a definitive answer
thank you for reading in this long message

 

[dlgoff]

When I was in school, check marks indicated correct. Note the 3 which to me indicates correct points earned.

 

[Hyperfine]

but I have not found any other sources on the web showing that light travels from eyes to the image. And it makes no sense to me.

Emphasis added. That is good, because it should make no sense to you or anyone else.

 

[hutchphd]

The light is in fact coming from the Object to the eye. The (virtual) image appears along that line.

 

[Ibix]

but I have not found any other sources on the web showing that light travels from eyes to the image. And it makes no sense to me.

You are correct.

I suspect the person in the video thinks that light travels from object to image, which is true in the case of a real image such as a slide projector. The case in the question, however, is a virtual image and no light goes to the image at all and this mnemonic fails.

In any imaging system light must always go from the object to the eye (maybe bouncing off a screen or something). It can't go the other way. People's eyes do not glow.

 

[PeroK]

People's eyes do not glow.

But you can see someone else's eyes!

 

[Ibix]

But you can see someone else's eyes!

Fair point. Bet you can't see their retina, though.

 

[PeroK]

Fair point. Bet you can't see their retina, though.

An optician can, by shining a light in. Which reminds me, I need to book an eye test!

 

[berkeman]

Fair point. Bet you can't see their retina, though.

Some animals have retinas that reflect light, for better low-light vision...

https://www.northcountrypublicradio.../20180315/what-makes-some-eyes-shine-at-night

 

[Ibix]

Some animals have retinas that reflect light, for better low-light vision...

Sure, and you can see their eyes glowing.

I'll be more precise. Vision does not in any way depend on light coming from the eye that is doing the perceiving (the sole exception to that is when you look at a reflection of your own eye). Light always comes from the object to the eye or camera doing the viewing. So the video demo of the mark scheme is unequivocally wrong. I hope we can agree on that.

Eyes can be objects in such a system, but that is not the case here. Or at least it is not shown as such, and even if the object were to turn out to be an eye the video is wrong.

 

[Hyperfine]

If light came from our eyes, why can we not see well in the dark?

 

[hutchphd]

Plato had his reasons which certainly seem when illuminated by modern "wisdom".

 

[PeroK]

Plato had his reasons which certainly seem when illuminated by modern "wisdom".

This is why modern science trumps ancient philosophy any day!

 

[apostolosdt]

Plato had his reasons which certainly seem when illuminated by modern "wisdom".

Thomas Kuhn clarified that misconception years ago!

 

[lioric]

Thank you all for your contributions
I guess I can say that we have reached a consensus that light does not come from the eyes. And that when we draw ray diagrams, the light from an object goes to the image only in real images and not in virtual images. Thank you very much.

 

[russ_watters]

Some animals have retinas that reflect light, for better low-light vision...

Can you explain? How does a reflective retina improve low-light vision? I feel like that should be a detriment since that's light the retina isn't absorbing.

....or was that a joke I didn't get?

 

[renormalize]

Can you explain? How does a reflective retina improve low-light vision? I feel like that should be a detriment since that's light the retina isn't absorbing.

....or was that a joke I didn't get?

Google "tapetum lucidum". It's the reflective layer behind an animals retina that sends light back through the retina for a second opportunity for detection.

 

[sophiecentaur]

Google "tapetum lucidum". It's the reflective layer behind an animals retina that sends light back through the retina for a second opportunity for detection.

One could ask why all animals don't use this technique. I would think it would be to suppress multiple images formed by multiple reflections. After passing one receptor, a reflected ray could be scattered if the backing is not flat and it could be received by surrounding sensors. This would affect acuity, particularly with contrasty images. It's the usual compromise; improved low light vision for nocturnal animals and good acuity for daytime animals.