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Old Nov 10th 2009, 09:47 AM   #1
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Junior science problem

This is a junior science problem but I am not quite sure the answer

Look at the following right-most letter "O" carefully with your right eyes while your left eyes are covered by your hand. After a while, look from the number 1 to 10, then you will find that (according to the question) there is a number disappearing. What does this experiement show?

10 9 8 7 6 5 4 3 2 1 O



A. We have blind spot in our retina
B. The image O still remains in our brain after a while so it covers some letter

Which is the answer? A or B?
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Old Nov 10th 2009, 11:14 PM   #2
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I ve tried till ive gone squint eyed but nothing seems to be disappearing!

When you look from 1 to 10, do you have to use both eyes?. I tried that too.
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Old Nov 11th 2009, 12:08 AM   #3
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Originally Posted by physicsquest View Post
I ve tried till ive gone squint eyed but nothing seems to be disappearing!

When you look from 1 to 10, do you have to use both eyes?. I tried that too.
still using the right eyes while covering the left eye when looking from 0 to 10

This is a question extracted from an examination paper, so i think it should not be wrong
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Old Nov 11th 2009, 08:19 AM   #4
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read this long time ago in life sciences but still not sure. i read that there is a point on retina where optic nerve crosses and so devoid of photoreceptors.that is the blind spot which is not visible because surrounding photoreceptors produce image but blind spot does not. so image corresponding to blind spot is not formed.
however, u can easily answer this question without knowing all this. because none of the letters to the left of o resemble it except o itself. so o cannot obscure anything. so the blind spot option is correct, atleast to me.
it is obvious that the phenomenon will not appear on our computers because u typed them from keyboard and thus 0 is not at blind spot separation. please repeat it in the exam paper, i think you will see the left 0 missing.
if u need some detail, well , i confess i have chucked that book out. i hate biology.
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Old Nov 11th 2009, 10:41 AM   #5
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Originally Posted by r.samanta View Post
read this long time ago in life sciences but still not sure. i read that there is a point on retina where optic nerve crosses and so devoid of photoreceptors.that is the blind spot which is not visible because surrounding photoreceptors produce image but blind spot does not. so image corresponding to blind spot is not formed.
however, u can easily answer this question without knowing all this. because none of the letters to the left of o resemble it except o itself. so o cannot obscure anything. so the blind spot option is correct, atleast to me.
it is obvious that the phenomenon will not appear on our computers because u typed them from keyboard and thus 0 is not at blind spot separation. please repeat it in the exam paper, i think you will see the left 0 missing.
if u need some detail, well , i confess i have chucked that book out. i hate biology.
sorry

i still don't quite understand

in fact, what is blind spot??

In my understanding, in addition to the fact that blind spot has no rod cell or cone cell, when light focus at blind spot we can't form image (and consequently we can't see the object), but what is the purpose of looking at the rightmost O before we look from 1 to 10?

I have tried covering my left eye while looking from 1 to 10 without focusing on the rightmost "O" i still see all the number
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Old Nov 11th 2009, 06:19 PM   #6
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i dont know if this will help, (i contacted a friend who is bio -expert.)he asked u to visit wikipedia and type blind spot in the search bar and then follow the on screen instructions.below is the link.
however, please note, what i have said above is bound to be vague and imprecise beacuse i havent read the subject for years. good to see you are interested in such problems.thanks.
http://en.wikipedia.org/wiki/Blind_spot_(vision)

Last edited by r.samanta; Nov 12th 2009 at 11:31 PM.
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