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A converging lens produces a real inverted image of a pencil located 0.15 m from the lens. If the image produced is located 2.5 cm from the lens, then the lens's focal length is:
Title
A converging lens produces a real inverted
Your Result
Correct
Difficulty
Hard
Your Pace
0:01
Others' Pace
2:22
Text Explanation
15/7 cm.: This answer choice is correct. You can find the focal length by plugging in the values of the object distance and the image distance to the thin lens equation as follows:
1/f = 1/do + 1/di
1/f = 1/15 + 1/2.5
1/f = 7/15
f = 15/7
7/15 cm.: This answer choice is incorrect, because a focal length of 1/3 cm is too small. It corresponds to an image distance of 0.34 cm, not 2.5 cm.
1/3 cm.: This answer choice is incorrect, because a focal length of 7/15 cm is too small. It corresponds to an image distance of 0.48 cm, not 2.5 cm.
3 cm.: This answer choice is incorrect, because a focal length of 3 cm is too large. It corresponds to an image distance of 3.75 cm, not 2.5 cm.
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