Wave Interactions

Properties of Light

• Transparent – light can pass through completely

– Ex: glass

• Translucent – light can partially pass through (cloudy)

– Ex: wax paper

• Opaque – light cannot pass through

– Ex: thick cardboard

What is light?

• Light is the visible part of the electromagnetic (EM) spectrum

– It’s the only part we can see

– Light waves are transverse waves

• White light can be broken down into colors: ROY G BIV

How do we see?

• We see only light that reaches our eyes

• Objects absorb some colors and reflect others

– We see the colors that are reflected back

How do we make different colors?

• Waves combine through Interference

– Constructive Interference – when two waves combine to make a bigger wave

– Destructive Interference – when two
waves combine to make a smaller wave

• Colors can add together to make other colors

• Your TV set makes all colors using
Red, Green, and Blue

– RGB are the primary colors of light

– R + G + B = White

• These are Additive Color hues

– Red and Blue = Magenta (Purple)

– Blue and Green = Cyan (Aqua)

– Red and Green = Yellow

– Red + Green + Blue = White

Why are paints different?

• Paints use pigments to absorb some light and reflect others

– Remember: we see the reflected light

• Paints are Subtractive Colors

– Green paint absorbs all colors except green

– If you mix red and green:

• Red absorbs all but red (_OYGBIV)

• Green absorbs all but green (ROY_BIV)

• They subtract and you get an icky brown

• Cyan, Magenta, and Yellow are the primary pigments

• C + M + Y = Black (technically)

– Actually, you can’t make pure black using CMY, because some color still reflects

• Magenta + Yellow = Red

• Yellow + Cyan = Green

• Cyan + Magenta = Blue

• C + M + Y = Black