A) 7.5 cm
B) 22.5 cm
C) 40 cm
D) 30 cm
Correct Answer: A
Solution :
Image formation by concave mirror will be as follows: Given, \[m=\frac{image\,\,dis\tan ce}{object\,\,dis\tan ce}\,\,=\,\,\frac{\nu }{u}\,\,=\,\,2\] \[\Rightarrow \,\,\,\,\,\,\nu =-1u\] Also \[\frac{1}{f}=\frac{1}{\nu }=\frac{1}{u}\] Where f is focal length, v is image distance and u is object distance. \[\Rightarrow \,\,\,\,\,\,-\frac{1}{15}=\frac{1}{u}-\frac{1}{2u}=\frac{1}{2u}\] \[\Rightarrow \,\,\,\,\,\,u=-\frac{15}{2}\,\,=\,\,-7.5\,cm\] Thus, the object should be placed at a distance 7.5 cm in front of the mirror.You need to login to perform this action.
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