Candle Problem
You are in a dark room and seeing a lighted candle at 6-to-8 meters distance. Slowly move towards it till the candle is right in front of your eyes (a mm or two away). As you move towards the candle the eye stars accommodating to keep it in focus. This it can do to a certain maximum point beyond which the flame goes out of focus. Since the candle is still moving closer to the eye, its focus which till now was on the retina will keep going backwards, so much so that an inverted image formed on the retina should at one point become upright. Then why don’t we see objects which are very close to the eye, upside down?
WARNING: DON'T TRY THIS AT HOME, YOU CAN BURN YOUR EYE BROWS OR WORSE LOSE YOUR SIGHT
WARNING: DON'T TRY THIS AT HOME, YOU CAN BURN YOUR EYE BROWS OR WORSE LOSE YOUR SIGHT
Labels: funphysics, thinktank
posted by Rajesh Lal at
5:50 AM
17 Comments:
errr, because you don't see objects that are completely out if focus!
Maybe it has something to do with the mind knowing the image is not inverted ... and therefore, we still perceive the image in its correct orientation.
Experiments were performed with subjects wearing glasses which inverted their vision. After a peroid of time, their minds adjusted and re-inverted the image back to normal. Then, upon removing the glasses, images appeared inverted until their minds once again adjusted.
Our minds know how we normally, visually perceive images and it will adjust to maintain that perceived normality.
I say, you don't "see" with your eyes. Your eyes catch an image and transmit the matrix of colors to the brain. You eyes may catch and image, but it they aren't transmitted to the brain, you can't see.
You brain learns to recognize it receives. Thus it is the brain that sees, and it has learned to see the object with the “top” up.
I tried this at home, and my eye-balls burnt out at about 2mm. PLease warn others not to try this at home....
Actually, it is the brain that interprets the image as Ragknot says, and the brain collates the information as a recognisable image - ie correctly oriented candle.
Another interesting thought on perception is that you see the sky as blue. You are told it is blue from an early age. The colour you see is blue. I may see this as red, but the colours I choose for the sky when I paint are the same as you perceive as blue. Do we all interpret colours the same way?
I probably haven't expressed that well, but heck, I just roasted my eye-balls!
Interestingly (or maybe so just to me), the all images that the eyes take in are inverted already, and it is the brain that perceives them as "right side up" anyway...at least that is what I was taught.
Whe the object is very close to the eye, there is no image on the retina for the brain to do anything with.
Make a new born baby to do that, he should see it upside down, only problem is that he won't b able to tell you that.......unless u can understand baby talk :P
Apparently you can adapt to seeing upside down in a matter of a few days. Follow the link for more info.: http://wearcam.org/tetherless/node4.html
does the image fall on the blind spot?
Chris ... that's the type of experiment I was referring to ... in one of the tests, the subject, after removing the glasses, would see images inverted until his mind compensated and re-oriented the visual input, making things normal again.
It's an interesting experiment, and the answer is because of the self-defense mechanism our body regulates. The intensity of a flame is well above 50 CDs (measurement for light) and instead of projecting the image on the retina, the image goes directly on the iris. The brain can only read and interpret the images it finds on the retina, therefore, we see what our eyes see... :D
actually you do see stuff upside down then something in the brain switches it.
Aaaaarrghh - so what that the image is (normally) physically upside down? Of course the brain sorts that out for our perception. I can't imagine why practically everyone is harping on about that.
It is also unfortunate that a candle was specified as the object being observed. Instead, use an ordinary object in a lit room.
I've just tried bringing an upright pencil as close to my eye as I dare. The image appears the right way up, but becomes so blurred that it is no longer a recognisable image.
I believe that object would have to penetrate the cornea to get close enough to the lens for the image to invert. But it would be so blurred that you won't recognise the object.
Scratch my last paragraph - it's nonsense.
Hold your hand in front of your face, then slowly move your hand towards your face if ti starts to smell like ass, then go wash your hands.
Karl Sharman, you talked about color in your second to last paragraph, and I used to ponder the same thing. But think about what makes an object a certain color. It's not our mind seeing it, it's simply the object absorbing certain colors, and reflecting others. But saying "We could all perceive colors differently" isn't that crazy of an idea. Shades, tones, contrast, each eye can receive this all differently due to damage and uniqueness, but to say that what I call red you call yellow, that goes beyond our eyes and into the properties of the object itself.
Hi Karl and Mingo. We do seem to be able to agree that what I call yellow, you also call yellow (defective vision problems aside). Our mind interprets what we see. But what is interpreted is physical reality. All humans have the same bio-chemistry, so I expect that our mental processes will also be very similar. i.e. you see the same yellow that I see.
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