Focal Point:The point at which parallel rays of light converge after passing through a lens.
Lens Formula: $\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$, where $f$ is the focal length, $d_o$ is the object distance, and $d_i$ is the image distance.
Magnification:$M = \frac{h_i}{h_o} = -\frac{d_i}{d_o}$, where $M$ is magnification, $h_i$ is image height, $h_o$ is object height, $d_i$ is image distance, and $d_o$ is object distance.