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Explore the four ways waves interact with a medium and with other waves: reflection, refraction, diffraction, and interference. Understand the laws of reflection and refraction, the concept of diffuse reflection, the bending of waves through openings, and the combination of waves through interference.
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WAVES WAVE INTERACTIONS
FOUR WAYS WAVES INTERACT • REFLECTION • REFRACTION • DIFFRACTION • INTERFERENCE How waves interact with a medium How waves interact with other waves
LAW OF REFLECTION Angle of incidence = angle of reflection
We see from where we think the light ray is coming. Reversed image Non-reversed image
29.2The Law of Reflection Incident rays and reflected rays make equal angles with a line perpendicular to the surface, called the normal. • The angle between the incident ray and the normal is the angle of incidence. • The angle between the reflected ray and the normal is the angle of reflection. • Angle of incidence = Angle of reflection
29.4Diffuse Reflection Diffuse reflection allows us to see most things around us. • Light is diffusely reflected from paper in many directions. • Light incident on a smooth mirror is only reflected in one direction. Ordinary paper has a rough surface when viewed with a microscope.
29.8Refraction of Light As a light wave passes from air into water, its speed decreases.
CONCAVE AND CONVEX MIRRORS Convex mirror causes light rays to converge. Concave mirror causes light rays to diverge.
REFLECTION • The bouncing back of a wave when it meets a surface or boundary. • http://www.gmi.edu/~drussell/Demos/reflect/reflect.html • http://www.physicsclassroom.com/mmedia/optics/lr.html
REFRACTION • The bending of a wave as it passes from one medium to another. • http://www.physicsclassroom.com/mmedia/optics/lr.html Light from pencil moves from air to your eye, through water and glass to your eye, through plastic to your eye
DIFFRACTION • The bending of a wave as it passes through an opening or by an edge. • Ex.: Hear a voice from around the corner.
31.1 Diffraction and Huygens’ Principle The extent to which the water waves bend depends on the size of the opening.
INTERFERENCE • The combination of two or more waves that exist in the same place at the same time. • Constructive Interference (additive effect—in phase) • Destructive Interference (subtractive effect—out of phase) • http://users.erols.com/renau/wave_interference.html • http://www2.biglobe.ne.jp/%7Enorimari/science/JavaEd/e-wave3.html • http://www2.biglobe.ne.jp/%7Enorimari/science/JavaEd/e-wave2.html