13: Geometric Optics

Notes: Unit 13 Geometric Optics Slideshow

Textbook: Chapter 21-24

Objectives & Essential Knowledge: 

Geometric Optics

Tracing light paths

• • light rays help illustrate the path of light, especially before and after an interaction with matter (a boundary).

  • Light travels in straight lines when not changing medium

  • light rays can be traced backwards or forwards 

Reflection: bouncing of a light ray off of a surface

• • angle of incidence = angle of reflection for specular reflection

    • the angle is measured from the normal to the surface

  • diffuse reflection scatters light off of a rough surface because the normal lines to the surface are not in a consistent direction

  • specular reflection is when the normal lines align and produces a reflected image.  

Refraction:  speed change bends light according to snell's law

• • • Light bends towards normal when going optically slower (more optically dense), away when higher

    • at a critical angle, when the light would be refracted at 90 degrees, light begins to totally internally reflect (no more refraction). 

•  Image formation

  • reflection causes images to form with curved mirrors.

  • refraction causes images to form with curved lenses.

  • use ray diagrams to predict size, orientation and location of images formed.

  • use the thin lens equation to predict size, orientation and location of images formed. 

  • Predict whether an image will be virtual or real.

Common Misconceptions:

• Waves transport matter.

• There must be a medium for a wave to travel through.

• Waves do not have energy.

• All waves travel the same way.

• Different colors of light are different types of waves.

• Light just is and has no origin. 

• Light is a particle. 

• Light is a mixture of particles and waves.

• Light waves and radio waves are not the same thing.

• In refraction, the characteristics of light change. 

• The speed of light never changes.

• Rays and wave fronts are the same thing.

• There is no interaction between light and matter.

• The addition of all colors of light yields black.

• Double slit interference shows light wave crest and troughs.

• Light exits in the crest of a wave and dark in the trough.

• In refraction, the frequency (color) of light changes.

• Refraction is the bending of waves.