A short linear object of length b lies along the axis of a concave mirror or focal length f at a distance u from the pole of the mirror. The size of the image is approximately equal to

Options

A. `(f/(u-f))b`
B. `(f/(u-f))^(2)b`
C. `(f/(u-f))b^(2)`
D. `(f/(u-f))`

Answer

B

Explanation

(b) Using mirror formula,
`1/v+1/(-u)=1/(-f)`
Multiplying with u,
`u/v=(-u)/f)+1=(f-u)/f`
`therefore` Magnification, m=`v/u=(f/(f-u))`
Now, `abs(dv)=m^(2)abs(du)`
Sizze of image=`(f/(f-u))^(2)`cdotb`