A) - 407 cm
B) 250 cm
C) 125 cm
D) 25 cm
Correct Answer: A
Solution :
\[\frac{{{f}_{l}}}{{{f}_{a}}}=\frac{{{(}_{a}}{{\mu }_{g}}-1)}{{{(}_{l}}{{\mu }_{g}}-1)}\]; \[{{f}_{a}}=\frac{R}{2({{\mu }_{g}}-1)}=\frac{15}{2(1.6-1)}=12.5\] \[\Rightarrow \]\[\frac{{{f}_{l}}}{12.5}=\frac{(1.6-1)}{\left( \frac{1.6}{1.63}-1 \right)}\Rightarrow {{f}_{l}}=-\,407.5\]\[cm\]
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