A) 20 cm (only)
B) 40 cm (only)
C) 30 cm (only)
D) 20 cm or 40 cm
Correct Answer: D
Solution :
[d]Here image can be real or virtual. If the image is real |
\[f=-\,30,\,u=?,\,m=-3\] |
\[m=\frac{f}{f-u}\Rightarrow -\,3\,=\frac{-\,30}{-\,30\,-\,u};\,\,u=-\,40\,cm\] |
If the image is virtual |
\[m=\frac{f}{f-u}\Rightarrow 3=\frac{-\,30}{-\,30\,-\,u}\Rightarrow \,u=-\,20\,cm\] |
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