A square wire of side `3.0 cm` is placed `25 cm` away from a concave mirror of focal length `10 cm`. What is the area enclosed by the image of the wire ? The centre of the wire is on the axis of the mirror, with its two sides normal to the axis.

Options

A. 2 `cm^(2)`
B. 4 `cm^(2)`
C. 8 `cm^(2)`
D. 16 `cm^(2)`

Answer

B

Explanation

As `(1)/(v)+(1)/(u)=(1)/(f)`
`:.(1)/(v)+(1)/(-25)=(1)/(-10)`
or `(1)/(v)=(-1)/(10)+(1)/(25)=(-3)/(50)`
or `v=(-50)/(3) cm`
As image is real,
`m=(-1)/(O)=(v)/(u) " " or " " I=-Oxx(v)/(u)`
or `I=-3xx((50)/(3))/(-25)=-2cm`(inverted)
`:.` Area of frame image`=(2)^(2)=4cm^(2)`