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Chapter 12.3
Reflection and Color
Angle of Reflection = Angle of Incidence
Balls bouncing on a pool table follow laws of reflection.
Rough surfaces reflect light in many directions, calledDIFFUSE REFLECTION
When the water is still, reflection is “clearer”
The image in the convex mirror (left) looks smaller. The images in the concave mirror (right) looks bigger.
How Objects React to light
Objects can be classified into three categories Opaque Transparent Translucent
Opaque Objects
Do not allow light to pass through them Examples are brick, carpet, wood, apple, etc. Objects appear the color they are because of
the color of light they reflect; all other colors are absorbed
Transparent Objects
Allow light to pass through them Items are “see-through” Examples are glass and cellophane Objects appear the color they do based on
the color/frequency of light they allow to pass through
Translucent Objects
Allow some light to pass through but scatters most of the light within it
Cannot see things clearly through a translucent object
Examples are a block of wax or a frosted light bulb
R O Y G B I V
Red Orange Yellow Green Blue Indigo Violet
White light
Triangular Prism
More on R O Y G B I V
Why is the apple red?
White light strikes the apple
All colors absorbed except red
Red light is reflected
Still More on R O Y G B I V
What color is the apple now?
Green light strikes the apple
Green light is absorbed. No color is reflected so apple appears black
Additive RGB Colors
Green
BlueRed
white
YellowCyan
Magenta
http://home.att.net/~B-P.TRUSCIO/COLOR.htm
Adding colors of LIGHT
CMY-Subtractive Colors
Magenta
CyanYellow
black
redblue
green
Pigments – they subtract specific colors of light, so you only see the colors that were not “subtracted”
Refraction, or bending of light as it moves from air to water
Angles are measured withrespect to the line which isperpendicular to theinterface.
When light travels from one medium--such as air, toanother one of higherdensity--such as water,usually the light ray bendstoward the perpendicularline.
Total Internal Reflection, as in fiber optic cables.
The critical angle for diamondin air is 24.5 degrees; any raywhich strikes the surface on theinside at an angle of greaterthan 24.5 degrees will notescape the diamond.
The Convex Lens as a Magnifier
