A) 30 cm and 60 cm
B) 30 cm and ? 45 cm
C) 45 cm and 90 cm
D) 15 cm and 45 cm
Correct Answer: B
Solution :
For achromatic combination \[\frac{{{f}_{1}}}{{{f}_{2}}}=-\frac{{{\omega }_{2}}}{{{\omega }_{1}}}=-\frac{0.036}{0.024}=-\frac{3}{2}\] and \[\frac{1}{{{f}_{1}}}-\frac{1}{{{f}_{2}}}=\frac{1}{90}\] solving above equations be get \[{{f}_{1}}=30cm,\ {{f}_{2}}=-45cm\]You need to login to perform this action.
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