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1. You are marooned on a desert island and want to use your eyeglasses yo start a fire. Can this be done if you are nearsighted? If you are a farsighted? EXPLAIN.
2. While lost in the mountains, a person who is very farsighted in one eye and barely farsighted in the other made a crude emergency telescope from the two lenses of his eyeglasses. How did he do this?
..thanks in advance for those who answered..(^^)
This is complete guess based on some knowledge
So Myopia (Nearsightedness) occurs when the lens focuses light from a DISTANT object in front of the retina.
Okay so a lens of the eye is a converging lens = () (try and imagine the parenthesis as connected and that's the shape of the lens).
Obviously with eye defects the lens is for a better work broke and doesn't converge light on to the retina properly.
Nearsightedness means you can see close objects but you can't see far objects. In fact what happens is light from distant objects is focused in front of the retina.
In order to compensate we have eye glasses which help bend the light to help the lens focus the light properly on the RETINA.
So for nearsighted people; if you use a DIVERGING lens you can bend the light rays outward just enough so that the eye lens will focus the light on the retina
Try and draw this if you know about rays.
Okay so obviously if you want to make fire you need to converge light to a single point. If you're glasses are made from a diverging lens then you can't focus light on a single point to create fire
If you're far sighted
Nearby objects are hard to see because light is focused BEHIND the retina. (Retina is AT THE BACK of the eye btw)
Okay so in order to try and compensate eye glasses are made of CONVERGING lenses and you could use them to make fire
I don't know about the telescope sorry. I'm pretty sure the above is true for lens but try wikipedia or yahoo search just to be sure.
Hey I was just curious and I searched and found this stuff listed under sources to kind of prove my stuff. Which is cool just to be able to think through it.
For the Telescope. Since Both lenses are converging lenses. I don't know which lens you would use in which position if you find the information I would love to know. But a telescope is made from two converging lenses. The objective lens and the eye piece.
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