1. Light waves interact with materials
Ch 3.4
Light waves interact with materials

2. Background Information
The electromagnetic (EM) spectrum is the range of all wave frequencies that are arranged by the length of the waves produced.
Examples from shortest to longest wavelengths:
radio waves, microwaves, infrared light (like thermal vision), visible light, UV light, x-rays, and gamma rays.

3. Background Information
Refraction is the bending of a wave as it crosses the boundary between two mediums at an angle.
Reflection is the bouncing back of a wave after it strikes a barrier.

4. Light can be reflected, transmitted, or absorbed
Transmission is the passage of an EM wave through a medium (or material).
Absorption is the disappearance of an EM wave into a medium.

6. How Materials Transmit Light
Transparent materials allow most of the light to pass through.
Translucent materials allow some of the light to pass through but it scatters and spreads the light out in all directions.
Opaque materials do NOT allow ANY light to pass through.

8. Scattering
Scattering is the spreading out of light rays in all directions, because particles reflect and absorb the light.
Fine particles in a material cause the light to spread out; example: air

10. Why is the sky blue?
Particles in Earth’s atmosphere, at that moment, is scattering the blue wavelengths of the visible light spectrum more than the other colors, making the sky appear to be blue.

12. Polarization
Polarization is a quality of light in which all of the waves vibrate in the same direction.

14. Wavelengths determine color
Prism is a tool that uses refraction to spread out the different wavelengths that make up white light.
Visible light is made
up of individual color
wavelengths.
R-O-Y-G-B-I-V

15. Color Reflection & Absorption
In anything you see, the wavelength that is reflected is the color(s) that your see.
All the other colors of the EM spectrum are absorbed (not seen).

16. Primary Colors of Light
The primary colors are red, blue, and green.
When all 3 colors are mixed together equally, they appear white, or colorless.
Mixing colors of light makes new colors by the addition of wavelengths.

17. Primary Pigments The primary pigments are yellow, cyan, and magenta.
When all 3 pigments are mixed together equally, they appear black, or the absence of reflected light.
Mixing colors of pigment makes new colors by the subtraction of wavelengths.