Optics lens problem

  • Thread starter Gshan12
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  • #1
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i need help!!

Given: A real object is located to the left of a convergent lens. The object's distance from the lens is 7/3f and its focal length is f. What is the image distance in terms of f?

I tried the formula 1/f = 1/di + 1/do... it didn't work :grumpy:
 

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  • #2
Doc Al
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Gshan12 said:
I tried the formula 1/f = 1/di + 1/do... it didn't work :grumpy:
What makes you think that doesn't work?
 
  • #3
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i got a weird fraction that di= (1-3f^2)/(f^2) and it's not one of the answer choices.
 
  • #4
Doc Al
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I don't see how you get [itex]f^2[/itex]. Redo it, carefully: [itex]o = 7f/3[/itex], so [itex]1/o = 3/(7f)[/itex]. [itex]1/i = 1/f - 3/(7f)[/itex], etc.
 
  • #5
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oh! i made a stupid math mistake...

THANK YOU SO MUCH!!
 

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