A) convergent lens of focal length 3.5 R
B) convergent lens of focal length 3.0 R
C) divergent lens of focal length 3.5 R
D) divergent lens of focal length 3.0 R
Correct Answer: A
Solution :
\[\frac{1}{f}=\left( \frac{1.5}{1.75}-1 \right)\,\,\left( \frac{1}{-R}-\frac{1}{R} \right)\] \[=\,\,\,\frac{-0.25}{1.75}\left( -\frac{2}{R} \right)\,\,=\,+\frac{2}{7R}\] \[f=+\frac{7R}{2}\,\,=\,\,+3.5R,\,\,converging\]You need to login to perform this action.
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