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Lenses questionby physicsdawg
Tags: lenses 
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#1
Aug308, 03:10 PM

P: 25

1. The problem statement, all variables and given/known data
An object is 18cm in front of a diverging lens that has a focal length of 12cm. How far in front of the lens should the object be placed so that the size of its image is reduced by a factor of 2.0? 2. Relevant equations 1/do + 1/di = 1/f m= di/do 3. The attempt at a solution i keep solving and getting 36 using those equations, but the answer says its 48 ...i donno how to get 48 1/18 + 1/di = 1/12 di=7.2 m= 7.2/18 m=.4 1/2m=0.2 .2= 7.2/do do=36 


#2
Aug308, 03:16 PM

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P: 2,688

Can you show your calculations, please? I can't find your mistake if I can't see your work.



#3
Aug308, 03:19 PM

P: 25

k i edited it



#4
Aug308, 03:30 PM

HW Helper
P: 2,688

Lenses question
Hmmm. I am also getting 36 as my answer. I know this is a stupid question, but are you sure your numbers are correct? It doesn't hurt to check. Also where are you getting the answer from?



#5
Aug308, 03:38 PM

P: 25

physics textbook



#6
Aug408, 06:46 AM

Sci Advisor
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Thanks
P: 26,157

Try using 8cm instead of 18cm. 


#7
Aug408, 11:06 PM

HW Helper
P: 2,249

Hi physicsdawg,
[tex] 0.2 =  di/do [/tex] and you need to find do. Do you see how to find it? 


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