AP Physics 2 / Unit 13: Geometric Optics
13.4 Images Formed by Lenses
Notes
Same equations as mirrors: $\displaystyle \frac{1}{f}=\frac{1}{d_o}+\frac{1}{d_i}$.
- Converging (convex) lenses: $f>0$; real images for objects beyond $f$.
- Diverging (concave) lenses: $f<0$; always virtual, upright, smaller.
Practice
An object at 20 cm from a converging lens with $f=10$ cm forms an image at:
$\displaystyle \frac{1}{10}-\frac{1}{20}=\frac{1}{20}$.
That image's magnification:
$\displaystyle -\frac{20}{20}$.
A magnifying glass uses a converging lens with the object:
Makes an upright, virtual, larger image.
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