1. Which color has the longest wavelength? 2. The shortest? 3. Which color has the highest frequency? 4. The lowest? 5. Which color has the most energy? 6. The least?

Quiz: Electricity and Magnetism

Behavior of Waves  Reflection  Refraction  Diffraction  Interference

Reflection  Reflection occurs when a wave bounces off a surface it cannot pass through.  Examples: echos, sonar, motion sensors, police radar  Important for architectural acoustics  Reflection of seismic waves allows scientists to determine the layered structure of the interior of the earth.

Reflection  The angle that the light approaches the mirror is called the angle of incidence.  The angle leaving the mirror is the angle of reflection.  The angle of incidence and the angle of reflection are equal.

Reflectors on the Moon Mythbusters: Reflectors on the moon 4:42

Refraction  Refraction is the bending of a wave as it enters a new medium at an angle.  Seismic waves bend as they move from the solid mantle to the liquid outer core.  Temperatures of layers affect how sound travels. It can be bent away from the ground (making it hard to hear) or towards the ground (making far sounds seem close).

Refraction  Examples:  Eyeglasses  Rainbow  magnifying glasses  Telescopes  ring around the moon or sun

Videos: Refraction Refractive Index: 3:09 Refraction: 2:07

Diffraction  Diffraction is the bending of a wave as it moves around an obstacle or passes through a narrow opening.  Examples: rainbow pattern on DVD’s, radio waves bend around buildings, pinhole camera, silver lining in clouds.  The fact that you can hear sound around corners and barriers is because of diffraction (and reflection.)

Diffraction  The amount of bending depends on the wavelength and the size of the opening.  Large obstacle, small wavelength = low diffraction  Small obstacle, large wavelength = large diffraction

Videos: Diffraction When water encounters a small opening: 2:39When water encounters an obstacle :34

Diffraction glasses When you look through these glasses you are looking through a special material called a diffraction grating. This grating is a piece of plastic that has many slit-like openings that are very narrow and closely spaced to each other. When light passes through these openings, it bends by an amount dependent on the type of light. For example, red light bends more than yellow light. When white light enters a diffraction grating, it separates into its constituent colors. These colors are the same as the spectrum of colors you see in a rainbow. This is similar to how a prism works. By Cmglee - Own work, CC BY-SA 3.0,

Pinhole camera By en:User:DrBob (original); en:User:Pbroks13 (redraw) - Public Domain,

Interference  Interference: when two or more waves overlap and then combine together.  Two types of interference:  Constructive: the waves combine to make a larger wave.  Destructive: the waves combine to make a smaller wave.

Videos: Interference Standing waves form if half a wavelength or multiples of half a wavelength fits exactly into the length of the vibrating cord. Examples: vibrating musical instrument strings. 1:21 :43

Exit ticket  Draw a simple diagram of: 1. Reflection 2. Refraction 3. Diffraction 4. Interference