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Old Nov 1st 2009, 05:59 PM   #1
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Optics - Reflection Help!

An object located in front of a concave mirror with a radius of curvature of 80 cm produced an inverted image that is three times the size of the object. What is the object distance?

1/f = 1/do + 1/di

hi/ho = -di/do

those are the 2 formulas we are given where:

f = focal point
do = distance object
di = distance image
hi = height image
ho = height of object

i have no clue on where to start and what formula i should be using...
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Old Nov 1st 2009, 09:02 PM   #2
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The focal length of the mirror is half its radius of curvature. Find f and just use the formulas you have shown.

You have hi/ho = 3 = - di/do .

Express either di or do in terms of the other , plug into the f equation and solve.
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Old Nov 1st 2009, 09:23 PM   #3
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ok so:

3 = - di/do
3do = -di

1/f = 1/do + 1/di

1/40 = 1/do + 1/3do

and then?
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Old Nov 1st 2009, 09:45 PM   #4
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nvm i got it. i forgot how to common factor but its all good.

thank you so much man! <3
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Old Nov 2nd 2009, 07:38 PM   #5
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Originally Posted by quick.on.my.feet View Post
ok so:

3 = - di/do
3do = -di

1/f = 1/do + 1/di

1/40 = 1/do + 1/3do

and then?
An object located in front of a concave mirror with a radius of curvature of 80 cm produced an inverted image that is three times the size of the object. What is the object distance?
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Old Nov 2nd 2009, 07:44 PM   #6
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Originally Posted by anwaar View Post
An object located in front of a concave mirror with a radius of curvature of 80 cm produced an inverted image that is three times the size of the object. What is the object distance?
An object located in front of a concave mirror with a radius of curvature of 80 cm produced an inverted image that is three times the size of the object. What is the object distance?
Ans:-
3d0/40=3d0/d0+3d0/3d0
3d0/40=3+1
d0=160/3 = 53.3cm
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Old Nov 2nd 2009, 07:45 PM   #7
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Originally Posted by anwaar View Post
an object located in front of a concave mirror with a radius of curvature of 80 cm produced an inverted image that is three times the size of the object. What is the object distance?
Ans:-
3d0/40=3d0/d0+3d0/3d0
3d0/40=3+1
d0=160/3 = 53.3cm
no job is too difficult
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Old Nov 5th 2009, 06:59 PM   #8
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i said i got it lol...
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