A) 45 cm
B) 30 cm
C) 7.5 cm
D) 22.5 cm
Correct Answer: C
Solution :
Focal length of concave mirror \[f=-15\,cm\] Magnification =2 (for virtual image) Linear magnification \[\text{m=}\frac{\text{size}\,\text{of}\,\text{image}}{\text{size}\,\text{of}\,\text{object}}\text{=-}\frac{}{\text{u}}\] \[2=-\frac{\upsilon }{u}or\,\upsilon =-2u\] Now, from the relation \[\frac{1}{f}=\frac{1}{\upsilon }+\frac{1}{u}\] or \[-\frac{1}{15}=\frac{1}{u}-\frac{1}{2u}\] or \[=\frac{1}{2u}\]You need to login to perform this action.
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