Unit: optics
Year: 1991 Question#: 98
Question: Base your answers to questions 97 and 98 on the diagram at the right which represents a convex lens being used to form the image of an object. The distance from the center of the lens to the object is 0.060 meter. The distance from the center of the lens to the image is 0.120 meter.
The focal length of the lens is
(1 ) 25 m
(2 ) 2.0m
(3 ) 0.12 m
(4 ) 0.04 m
What is this question really asking?
Explanation by: Jaques S.
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Answer 1
25 m
incorrect. this answer forgets to use 1/f (1 over the focal length) return to top
Answer 2
2.0 m
INCORRECT
return to top
Answer 3
.12 m
INCORRECT.
return to top
Answer 4
.04
CORRECT
Because 1/f=1/do+1/di return to top
What's this question really asking?
How do you find the focal length of a lens? return to top
