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Waves Interactions . Coach Medford Building Science Champions . In thought . On a separate sheet of paper, explain how you use waves in your daily life. . Objectives. Identify and compare reflection, refraction and diffraction Describe the two types of interference of waves. Key Terms .
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Waves Interactions Coach Medford Building Science Champions
In thought • On a separate sheet of paper, explain how you use waves in your daily life.
Objectives • Identify and compare reflection, refraction and diffraction • Describe the two types of interference of waves
Key Terms • Absorption • Transmission • Reflection • Angle of incidence • Angle of reflection • Law of reflection • Refraction • Diffraction • Interference • Constructive interference • Destructive interference
Interaction of Waves with Matter • Waves interact with matter in numerous ways • Waves can be: • Reflected by matter • Change direction when passing through a new medium • Transfer energy to matter • Such as sound waves being absorbed in padded walls • Interact with other waves • Overlap and form new waves • New wave has different properties from the original
Absorption Glass absorbs a small amount of energy allowing light to pass through the glass • Absorption – is the transfer of energy by a wave to the medium through which it travels • The amount of energy absorbed depends on the type of wave and material in which it moves • All materials absorb electromagnetic waves, although some materials absorb more electromagnetic waves than others Chrome looks shiny because it reflects light Black paint absorbs all the energy carried by light waves
Transmission • Transmission – the passage of light through an object • Plastic wrap allows almost all light to pass through it so you can see through it because very little energy is captured • Black construction paper absorbs almost all light energy which prevents you from seeing through the paper • Why do you believe some states restrict tint on windows? Window tint
Reflection • Reflection – the bouncing of a wave off a surface • An object that reflects all visible light appears white, while an object that reflects no visible light appears black • Light, sound, and water waves can reflect when they hit a surface
Law of Reflection • All types of waves can be reflected when they hit a surface • The angle at which a wave hits a surface is the same at which it bounces off the surface • Angle of incidence – angle between the incoming wave and the imaginary perpendicular line (normal) • Angle of reflection – angle between the reflected wave and the imaginary line (normal) • The angle of incidence and the angle of reflection are equal • This rule is called the law of reflection Angle of incidence Angle of reflection
Refraction • Refraction – the change in direction of a wave that occurs as the wave changes speed when moving from one medium to another • The greater the change in speed, the more the wave changes direction • The speed of sound waves is about three-fourths the speed of light waves in air • When light waves slow down they change direction
Diffraction • Diffraction – the change in direction of a wave when it travels by the edge of an object or through an opening • Sound waves spread out as they travel through a doorway because their wavelengths are roughly the same width as the doorway • The wavelengths of light waves are more than a million times smaller than the width of a doorway. As a result, these waves do not spread out as they travel through a door
Pictures of Diffraction • The waves are traveling down and then hit a barrier. Once they pass through the barrier they begin to expand again. • Water waves spread out from a narrow gap. The narrower the gap, the greater the proportion of diffracted waves.
Interference • Interference – occurs when waves that overlap combine, forming a new wave • Constructive interference – occurs when crest overlap crest or troughs overlap troughs • Destructive interference – occurs when a crest of one wave overlaps the trough of another wave
Interference Comparison The black line overlaps the crest and trough of the blue and red line The crest of the red line overlaps the trough of the blue and black line
Review • Waves can act in a variety of ways • Diffraction can happen in a variety of ways • Angle of incidence is equal to the angle of reflection