1. Geometric Optics
TEST: 12 April 2016

2. The Law of Reflection

3. Reflection Light behaves in a very predictable manner
Light can only travel in a straight line (most of the time…)
The Law of Reflection states that the INCIDENT (incoming) light’s angle will be exactly the same as the reflecting light’s angle

4. Reflection
This angle is always measured from an imaginary line Perpendicular to the plane of the mirror
This will be of more importance when we discuss curved or spherical mirrors

5. Reflection All objects reflect light Not all objects produce an image
Specular Reflection: occurs on smooth surfaces, all light reflects at the same angle (since it strikes the surface at the same angle), produces a clear image

6. Reflection
Diffuse reflection: occurs on rough surfaces, light scatters (as the incident light will hit the surface at many different angles), produces blurry, unclear, or no image at all

7. Types of materials Transparent: completely see-through
Translucent: See-through, cloudy
Opaque: Cannot see through

8. Refraction and Snell’s Law
Quiz tomorrow!!

9. Refraction
When light (or any wave) reaches a boundary between two mediums, refraction occurs
As the wave changes medium, its speed changes due to a change in density of the medium
This causes the light to bend, or change course

10. Refraction and sight As light travels, it moves in a straight line
When it changes medium, refraction can bend that straight line slightly
This is why objects in water tend to have distorted images and position
Our eyes and brains assume the light have traveled in a straight line

12. Index of Refraction
How much light speeds up or slows down depends on density
The denser the medium, the slower the speed
The index of refraction is a ratio that relates the new speed to the speed of light in a vacuum, which is constant

13. Indices of Refraction

14. Bending The direction the light bends is always related to the normal
More dense to less dense: Light moves faster, light bends AWAY from the normal
Less dense to more dense: light moves slower, light Bends toward the normal

15. Snell’s Law
We can relate the two materials using snell’s law, in order to find the refracted angle

16. Example: Light travels from air into an optical fiber with an index of refraction of 1.44.  (a)  In which direction does the light bend?  (b)  If the angle of incidence on the end of the fiber is 22o, what is the angle of refraction inside the fiber?  (c)  Sketch the path of light as it changes media.

17. Total Internal Reflection
As the angle of refraction approaches 90°, something happens
Instead of leaving the medium, the light is reflected back into the original medium
This is called total internal reflection and is the basic idea behind fiber optic cables