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Finding the height of an image reflected through a lens?

  • Thread starter surfahgirl
  • Start date
  • #1

Homework Statement



A 2.0--tall candle flame is 2.1 m from a wall. You happen to have a lens with a focal length of 37 cm .

How many places can you put the lens to form a well-focused image of the candle flame on the wall?

For each location, what are the height and orientation of the image?

Homework Equations



1/f=1/s'+1/s

h'=(s'/s)h

The Attempt at a Solution



So I think there are 2 places you can place the lens because s'+s=210cm and s' and s are interchangeable or something like that. I'm not quite sure though.

But then for the second part, i found the heights to be .65 and 6.2 cm but either one or both are wrong. I know I have to find the values for s and s' and I'm not quite sure how to do that. I thought s' would just be 2.1 but how can you have two values for it then?

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
rl.bhat
Homework Helper
4,433
5
Put s' = 210 - s and substitute it in the lens formula to find s.
 
  • #3
ah..just realized that myself.
that's so simple. i was definitely over thinking it.

thanks!
 

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