Lenses and optics: solving for focal point.

[ilovedeathcab]

Lenses and optics: solving for focal point. (SOLVED)

(2 points, penalty of 0.5)
When a flower pot is placed 1.2 meters on the left of a magnifying glass (converging lens), an image is formed on a screen 0.37 meters to the right of the lens. Find the focal length of the lens. Give your answer ...

* in terms of meters. Do not include units in your answer. They will be assumed to be meters.
* to a precision of hundreths of a meter. Use a format like #.## in your answer.
* to an accuracy of 0.02 m. Answers within 0.02 meters of the correct answer will be tolerated.

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I know that with a converging lens, the focal point value will be positive.
I started with the basic equation
1/f = 1/do + 1/di

1/f = 1/1.2m +1/.37m
f = .833333333m + 2.7027m

f = 3.536 m
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I entered this value and it counted it as incorrect. can somebody please tell me what I'm doing wrong? i would appreciate it. thanks ! http://moodle.oakwood.k12.oh.us/file.php/72/Unit_13_quiz_images/quiz13q3.jpg

 

[rl.bhat]

f = 3.536 m
This should be
1/f = 3.536