| Topic: |
Science > Physics |
| User: |
"MinionofLesrac" |
| Date: |
05 Jun 2004 05:15:40 PM |
| Object: |
Two Questions on Light |
These should be rather easy ( high school level ). Any help would be
appreciated.
1)Suppose the "relaxed" focal length f of the effective thin lens of
the eye is 2.55 cm. If an object is located at a distance p = 41.7
cm, what focal length f ' of the effective thin lens is required for
the object to be seen clearly?
2)White light hits a converging lens. The lens will focus the white
light at a point called the focus, but, if you look carefully, you
may find that not all the colors of light are focused at the same
point. Remembering that higher frequency of light is slower in glass
than low frequency light, rank the following colors in order of which
is focused farthest from the lens.
Put your answer in the following format
g>r>o>i>v>y>b:(this answer would indicate that
green is focused farthest from the lens).
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| User: "Jon Bell" |
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| Title: Re: Two Questions on Light |
05 Jun 2004 11:50:53 PM |
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In article <40c2460c$1_1@127.0.0.1>,
MinionofLesrac <SoulBlazze@yahoo-dot-com.no-spam.invalid> wrote:
These should be rather easy ( high school level ). Any help would be
appreciated.
1)Suppose the "relaxed" focal length f of the effective thin lens of
the eye is 2.55 cm. If an object is located at a distance p = 41.7
cm, what focal length f ' of the effective thin lens is required for
the object to be seen clearly?
Hint #1: When the eye is "relaxed", an object at infinity produces an
image at the back of the eyeball (assuming the person doesn't need
eyeglasses).
Hint #2: With the object at 41.7 cm, where must the image be located,
assuming we're talking about the same person, with the same eyeball?
2)White light hits a converging lens. The lens will focus the white
light at a point called the focus, but, if you look carefully, you
may find that not all the colors of light are focused at the same
point. Remembering that higher frequency of light is slower in glass
than low frequency light, rank the following colors in order of which
is focused farthest from the lens.
Hint #1: How is the speed of light in glass related to the index of
refraction of the glass?
Hint #2: How is the index of refraction of the glass related to the focal
length of the lens? Does a larger index of refraction produce a longer
or shorter focal length, assuming the size and shape of the lens remains
the same?
--
Jon Bell <jtbellm4h@presby.edu> Presbyterian College
Dept. of Physics and Computer Science Clinton, South Carolina USA
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| User: "Sam Wormley" |
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| Title: Re: Two Questions on Light |
05 Jun 2004 05:56:38 PM |
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MinionofLesrac wrote:
These should be rather easy ( high school level ). Any help would be
appreciated.
1)Suppose the "relaxed" focal length f of the effective thin lens of
the eye is 2.55 cm. If an object is located at a distance p = 41.7
cm, what focal length f ' of the effective thin lens is required for
the object to be seen clearly?
Thin Lens Formula
http://scienceworld.wolfram.com/physics/ThinLensFormula.html
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