The focal length of each of the lens is 20 cm and the separation between them is 60 cm. What will be the position of image of a distance object formed by the combination by using thin lens formula separately for the two lenses?
A) - 40 cm
B) - 30 cm
C) + 30 cm
D) + 40 cm
E) + 20 cm
Correct Answer: D
Solution :
The first image will be formed at the form of the first lens. In this case, u = - 40 cm from the second lens. For second lens. \[\frac{1}{v}=\frac{1}{u}+\frac{1}{f}=\frac{-1}{40\,cm}+\frac{1}{20\,cm}\] \[\Rightarrow \] \[v=40\,cm\] The final image in formed at 40 cm to the right of second lens.
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