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Reflection. LIGHT Principles of Physics. Representing Light Waves. It is impossible to see the actual wave shape (crests and troughs, etc) of a light wave Instead we draw straight lines, called RAYS , that show the direction and path followed by the light. Representing Light Waves. Rays:
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Reflection LIGHT Principles of Physics
Representing Light Waves It is impossible to see the actual wave shape (crests and troughs, etc) of a light wave Instead we draw straight lines, called RAYS, that show the direction and path followed by the light
Representing Light Waves Rays: • Show wave path and direction • Are always straight lines • Are incident when incoming • Are reflected when they bounce back • Are refracted when transmitted at a new direction
Reflection We see objects because light reflects off of them into our eyes
Reflection Smooth surface – all rays reflect at same angle Reflection and Mirrors Rough surface – all rays reflect at different angles
Representing Light Waves Direction of a light ray is indicated by an angle from a line perpendicular to the surface where the light hits
Angle of Incidence • Angle of light coming toward the surface • Incident = incoming Normal Incident Ray i
Law of Reflection The angle of incidence, θi, equals the angle of reflection, θr θi= θr θi θr
Normal Line • Line perpendicular to the surface where the light hits Normal line 90˚ Light ray
Measuring with the Protractor Normal line • Position the protractor such that the center hole is located where the normal line and the light hits the surface (the zero line should be on the normal line) • Determine the angle from the normal line to the light 40˚ Light ray 90˚ Measuring Angles Game
Drawing with the Protractor Normal line • Predict where the light will go once it reflects • Position the protractor such that the center hole is located where the normal line and the reflected light leaves the surface(the zero line should be on the normal line) • Locate the angle of reflection starting from the normal line. • Draw the reflected ray from the surface at your measured angle using a ruler 40˚ Light ray 90˚
Plane Mirrors Straight, flat mirrors Images: • Appear to be behind the mirror (virtual) • Same size as object • Same distance behind mirror that object is in front • Right-left reversed