A concave mirror of focal length `15 cm` forms an image having twice the linear dimensions of the object. The position of the object when the image is virtual will be

Options

A. `22.5cm`
B. `7.5 cm`
C. `40 cm`
D. `30 cm`

Answer

B

Explanation

Image formation by concave mirrorr will be as follows
Given, `m=("image distance" )/("object distance" ) = -(v)/(u) = 2`
`implies v = -2u`
Also`(1)/(f)=(1)/(v)+(1)/(u)`
where `f` is focal length, v is image distance and `u` is object distance.
`implies-(1)/(15)=(1)/(u)-(1)/(2u)=(1)/(2u)``impliesu=-(15)/(2)=-7.5cm`
Thus, the object should be placed a a distacne `7.5 cm` in front of the mirrorr.