A) 15 cm
B) 10 cm
C) 20 cm
D) 5 cm
Correct Answer: A
Solution :
We know, \[m=\frac{{{h}_{i}}}{{{h}_{0}}}=\frac{-v}{u}\] Here, \[m=3,v-u=40\,cm\] So, \[m=\frac{-v}{u}\]or, \[-m=\frac{v}{u}\] or, \[-m-1=\frac{v}{u}-1\] or, \[-3-1=\frac{40}{u}\] or, \[-4=\frac{40}{u}\] or, \[u=-10\,cm\] \[\therefore \]\[v-u=40\,cm\] or \[v+10=40\,cm\] or, \[v=30\,cm\] We know, \[\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\] So \[f=\frac{uv}{u+v}\] or \[f=\frac{-300}{20}=-15\,cm\]You need to login to perform this action.
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