1. Wave Interactions Chapter 18

2. Properties of Waves Reflection – ability of a wave to bounce off a surface it cannot pass through –Angle of Incidence – angle at which a wave hits an object –Angle of Reflection – angle at which a wave bounces off an object Law of Reflection – angle of incidence = angle of reflection

3. Properties of Waves Incoming Wave Reflected Wave Angle of incidence Angle of reflection “normal”

4. Properties of Waves Refraction – bending of a wave as it enters a different medium –This happens for all waves, not just light –Light bends when it hits a prism and splits into separate colors

5. Properties of Waves Diffraction – bending of waves around a barrier

6. Properties of Matter 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

7. 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

8. 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 absorbed reflected

9. 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 Wave Superposition Principle: Interference of Two Transverse Waves

10. How do we make different colors? 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 Light: Constructive Interference

11. How do we make different colors These are Additive Color hues –Red and Blue = Magenta (Purple) –Blue and Green = Cyan (Aqua) –Red and Green = Yellow –Red + Green + Blue = White

12. 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

13. Why are paints different? 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 Paint: Destructive Interference

14. Why are paints different? Magenta + Yellow = Red Yellow + Cyan = Green Cyan + Magenta = Blue C + M + Y = Black