LIGHT Principles of Physics

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

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

We see objects because light reflects off of them into our eyes

Smooth surface – all rays reflect at same angle Reflection and Mirrors Rough surface – all rays reflect at different angles

Direction of a light ray is indicated by an angle from a line perpendicular to the surface where the light hits

 Angle of light coming toward the surface  Incident = incoming Normal Incident Ray i

The angle of incidence, θ i, equals the angle of reflection, θ r θ i = θ r θiθi θrθr

 Line perpendicular to the surface where the light hits Light ray 90˚ Normal line

1. 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) 2. Determine the angle from the normal line to the light Light ray 90˚ Normal line 40˚ Measuring Angles Game

1. Predict where the light will go once it reflects 2. 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) 3. Locate the angle of reflection starting from the normal line. 4. Draw the reflected ray from the surface at your measured angle using a ruler Light ray 90˚ Normal line 40˚

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