1. Electromagnetic Waves

2. Electromagnetic Wave Properties
Electromagnetic waves do not need a medium to propagate. They can travel in a vacuum.
The speed of all electromagnetic radiation in a vacuum is a constant.
c = 3 X 108 m/s.

3. Electromagnetic Spectrum
Draw out the spectrum noting trends in frequency, wavelength, wave speed and energy.
There is a easy mnemonic to help you remember the order of EM radiation….
Red Martians Invade Venus Using X-ray Guns
Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma
Wavelength…Starts Long and gets shorter towards Gamma
Frequency……Starts Low and gets higher towards Gamma
Speed is the same for all EM waves
Energy…Starts low and gets higher towards Gamma

4. Visible Light Colors Addition vs. Subtraction of Color
The perceived color of an object is due to two processes, addition and subtraction of colors.
The addition of color is the projection of various intensities of the primary colors of light to produce the desired color.
The subtraction of color is the absorption of specific colors by pigments. The colors that remain produce the desired color. The reflection of white light off a colored object is an example of color subtraction.

5. Visible Light Primary and Secondary Colors Light-Additive
Primary Colors:
Red
Green
Blue
Secondary Colors:
Cyan
Yellow
Magenta
Pigments-Subtractive
Primary Colors:
Cyan
Yellow
Magenta
Secondary Colors:
Red
Green
Blue

6. Visible Light Color Examples
Stare blankly at a colored object for a minute.

7. Visible Light

8. Visible Light Color Examples
Stare blankly at a colored object for a minute.

9. Visible Light

10. Reflection Definition of Reflection The turning back of a wave.
Law of Reflection
Angle of Incidence = Angle of Reflection.
i = r
 or ‘theta’ is a symbol used to denote a variable angle.
(It is like ‘x’ in algebra.)

11. Refraction Definition of Refraction Definition of Index of Refraction
The bending of a wave disturbance as it passes at an angle from one medium to another due to a change in speed.
Definition of Index of Refraction
The ratio of speed of light in a vacuum to its speed in a given transparent medium.   

12. Index of Refraction of Common Items
Vacuum
Air
(we round to 1.0)
Water
Common Glass 1.5
Diamond 2.42

13. Refraction Bending Rules The ray bends towards the normal, ni < nr.
Light traveling from a less dense to more dense medium slows down.
The ray bends towards the normal,
ni < nr.
Light traveling from a more dense to less dense medium speeds up.
The ray bends away from the normal,
nr < ni.   

14. ni sini = nr sinr Snell’s Law n = index of refraction  = angle
i = incident ray
r = refracted ray

15. Example #1
What is the index of refraction of a medium in which the speed of light is 1.85 X 108 m/s?

16. Example #2
A fisherman shines a flashlight at a fish swimming underwater. If the refracted ray makes an angle of 35.0 with normal, what is the angle of incidence? 

17. Total Internal Reflection
Definition of Total Internal Reflection
The complete reflection of light at the boundary of two transparent media. The effect occurs when the angle of incidence exceeds the critical angle for a light ray going from a more dense medium to a less dense medium.
Definition of Critical Angle
The minimum angle of incidence for which total internal reflection occurs. This occurs when the angle of refraction becomes 900.

18. Lenses Convex Lens Converging Lens Focal Point Focal Length Real Image
Location at which rays parallel to the principal axis converge to or appear to diverge from for a convex or concave lens respectively.
Focal Length
Distance from the focal point to the center of the lens.
Real Image
An image formed when rays of light actually intersect at a single point.

19. Lenses Concave Lens Diverging Lens Focal Point Focal Length
Location at which rays parallel to the principal axis converge to or appear to diverge from for a convex or concave lens respectively.
Focal Length
Distance from the focal point to the center of the lens.
Virtual Image
An image formed by light rays that only appear to intersect

20. Ray Diagram
Rules for Lenses

21. Ray Diagram Lens Trends Case Converging or Convex Lens
Diverging or Concave Lens
Size
Orientation
Image
do > 2f
do = 2f
2f > do > f
do = f
do < f

22. Converging or Convex Lens Diverging of Concave Lens
Ray Diagram
Lens Trends
Converging or Convex Lens
Diverging of Concave Lens
Focal Length
Object Distance
Image
Distance
Real Image
Virtual Image
Object Height
Image Height

23. Lens Equation
do= object distance
di = image distance
f = focal length

24. Example #4
Example #4
If an object is placed 15 cm in front of a converging lens with a focal length of 10 cm, how far from the lens should the card be placed in order to find a clear image?

25. Interference Interference Diffraction Polarization Doppler Effect
Pattern of constructive and destructive interference.
Diffraction
The spreading of waves into a region behind an obstacle.
Polarization
The alignment of electromagnetic waves.
Doppler Effect
A frequency shift that is the result of relative motion between the source of sound waves and an observer.