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

29.2 The 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 5

Ordinary paper has a rough surface when viewed with a microscope. 29.4 Diffuse 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. 6

29.8 Refraction of Light As a light wave passes from air into water, its speed decreases. 7

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. 13

Using diffraction gratings

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