Lecture 35

Readings

http://umdberg.pbworks.com/w/page/73088573/Lenses%20%282013%29

http://umdberg.pbworks.com/w/page/73088579/Lens%20equations%20%282013%29

http://umdberg.pbworks.com/w/page/125712593/Workout%3A%20Lens%20equations

https://www.physicsclassroom.com/Physics-Interactives/Reflection-and-Mirrors/Optics-Bench/Optics-Bench-Interactive

Lenses

• 3 Main rays

  

  

  • 1.) parallel to axis , then through $f$$f$ on far side
  • 2.) Through $f$$f$ on near side, then parallel to axis
  • 3.) Straight through center

• If object closer than $f$$f$ :

• Diverging Lense

  • Image always on same side as object
  • Image always upright and smaller and closer to lense

• Equations

  $$\frac{1}{f}=\frac{f}{i}+\frac{1}{o}$$

  

  • Positives:

    • $o$$o$ in front of lense
    • $i$$i$ behind lense
    • $f$$f$ if converging lense

  • Otherwise use negative sign

  • Note : "front" is where the light is coming from ( the actual , physical object )

• So same equation as for mirrors , but different convention for signs

• Image size:

  $$\frac{h^{{}^{\prime }}}{h}=\frac{i}{o}$$
  • If $h^{{}^{\prime }}$$h^{'}$ is positive , image is upside down ( same as mirror )

Clicker Questions