Past exam of the physics course of the year 1 of the natural sciences course of the University of Cambridge / 2021 / Section B / 9 / d

For $u=8\mathrm{cm}$ and negative focal length $f=-8\mathrm{cm}$,The transverse magnification is $M=-v/u=+1/2$, soThus the virtual image is upright, half the object's height, and $4.0\mathrm{cm}$ from the lens on the object's side. A parallel incident light ray diverges after the lens as though it originated at the near optical focus; the central light ray continues undeviated in the ideal thin lens model. Their backward extensions meet at the image tip, $(-4,1)\mathrm{cm}$.