Lecture 33

Readings

http://umdberg.pbworks.com/w/page/73088519/Basic%20principles%20of%20the%20ray%20model%20%282013%29

http://umdberg.pbworks.com/w/page/52627471/Flat%20mirrors

http://umdberg.pbworks.com/w/page/125511563/Workout%3A%20Flat%20mirrors

http://ophysics.com/l.html

http://ophysics.com/l9.html

https://www.geogebra.org/material/iframe/id/gncjry38/width/1088/height/561/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/true/rc/false/ld/false/sdz/false/ctl/false

GeoGebra Mirror Stuff = https://www.one-tab.com/page/xEkOGTR1SWeOqWJ54hwhhA

Ray Model

• Ordinary surfaces:

  

  • People at many locations can "see" the wall by seeing light coming off the wall
  • They can also see the light bulb if they look directly at the light bulb
  • However, they can't see the light bulb by looking at the wall

• Mirrors / Reflective Surface

  

  • Light from bulb hitting mirror at 1 spot only "bounces" in 1 direction
  • If you're standing in one location , you can only see the light bulb's reflection by looking at one specific spot on mirror
  • You can "see" the light bulb in the mirror
  • But if the room were dark, you couldn't see the rest of the mirror

  

  • Refraction (light ray going from 1 clear medium (like air) to a different clear medium (like water))

    

    • $I$$I$ stands for incident (incoming) light

    • $T$$T$ stands for transmitted light

    • $n_I$$n_I$ = index of refraction for air

    • $n_T$$n_T$ = index of refraction for water

    • Rule:

      • $n_I\ast sin({\theta }_I)=n_T\ast sin({\theta }_T)$$n_I * sin(\theta_I) = n_T * sin(\theta_T)$
      • This is "Snell's Law"

  

Flat Mirror

• Object appears to be "behind mirror":

• Ray tracing to find image (activity)

• The back-projected path is where the eye "thinks" the light is coming from
• The brain assumes light travels in straight lines