A) \[30\] \[cm,\]\[-60\]\[cm\]
B) \[20\]\[cm\], \[-30\]\[cm\]
C) \[15\]\[cm,\] \[-20\]\[cm\]
D) \[12\] \[cm,\] \[-15\]\[cm\]
Correct Answer: B
Solution :
\[\frac{1}{60}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}\] ?(i) and \[\frac{1}{30}=\frac{1}{{{f}_{1}}}+\frac{1}{{{f}_{2}}}-\frac{10}{{{f}_{1}}{{f}_{2}}}\] ?(ii) On solving (i) and (ii) \[{{f}_{1}}{{f}_{2}}=-\,600\] and \[{{f}_{1}}+{{f}_{2}}=-10\] Hence \[{{f}_{1}}=20\]\[cm\] and \[{{f}_{2}}=-30\]\[cm\]You need to login to perform this action.
You will be redirected in
3 sec