A) 21 cm
B) 42 cm
C) 63 cm
D) 84 cm
E) None of these
Correct Answer: C
Solution :
For achromatic combination, \[\frac{{{\omega }_{1}}}{{{f}_{1}}}=-\frac{{{\omega }_{2}}}{{{f}_{2}}}\] \[\therefore \] \[{{f}_{2}}=-\frac{{{\omega }_{2}}}{{{\omega }_{1}}}{{f}_{1}}\] \[=-\,\frac{0.21}{0.14}\times 42=-63\,cm\]You need to login to perform this action.
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