WARM UP 11/5/15 In your IAN notebook, solve the following problem. Show ALL of your work including the formula you used and the units of the answer. A tree 2736 ft. away from your position is struck by lightning. If you hear the thunder 2.5 seconds after the lightning hit, what is the speed of sound in this air?

Wave Interactions

6 Wave Interactions When a wave encounters a surface, 6 interactions can occur Interference Diffraction Reflection Absorption Refraction Polarization

Interference Interference – when two or more waves meet in the same medium Constructive Interference – when two waves add up to make a larger amplitude wave Destructive Interference – when waves add up to make a smaller or zero amplitude wave (cancel each other out)

Constructive Interference

Constructive Interference Crest to Crest Trough to Trough

Destructive Interference

Destructive Interference Crest to Trough

Check for Understanding! 1. 2.

Result of Interference Resonance – occurs when vibrations travelling through an object match the object’s natural frequency Also occurs when one object vibrates another object without touching it

Result of Resonance

Tacoma Narrows Bridge collapsing Result of Resonance Glass shattering Tacoma Narrows Bridge collapsing Chinook Helicopter

Reflection Reflection – when a wave bounces off a material and goes in a new direction

Refraction Refraction – when a wave passes through a different material and bends

Refraction

Diffraction Diffraction – when a wave bends around corners

Absorption Absorption – when a wave is absorbed by the material and may disappear

Polarization Polarization – when EM waves move through a filter that blocks one direction of the wave. VIDEO