1. Wave
Disturbances

2. In talking about the fundamental nature of light, we assume that light tends to travel in a straight line, unless it is acted on by some external force or condition. The obvious next question is, "What kinds of forces or conditions can affect light, and how?"
REFLECTION
When light “bounces” off of a surface and continues to travel outward at an angle, we call this Reflection.
Reflection from a smooth surface
Reflection from a rough surface
Reflection from a convex surface
Reflection from a concave surface
The straighter and smoother a surface is, the more accurate it will be in reflecting the original array of light waves.

3. REFRACTION
When light travels through a new medium in which it’s path is “bent”, we call this Refraction. Note: Light cannot travel through just anything. Something that light passes through is typically referred to as a lens of some sort. This always results in a slowing down of light speed.
You can test this concept by placing a straw or a pencil in a glass of water. The water as well as the glass itself act as a lens to bend light.

5. Wave patterns change as they encounter an obstacle.
DIFFRACTION
Diffraction is the bending of light as it passes the edge of an object or through a small opening. An example of this property is a shadow. If observed carefully, the edges of shadows are not solid, but slightly fuzzy.
Wave patterns change as they encounter an obstacle.
The closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk.

6. Sound Waves Behave Similarly in Many Cases:
When a sound wave hits a barrier it bounces back; the reflected wave is up side down to show that the reflected wave is "out of phase" with the source wave.
This is why you hear an echo when you shout in a large room or a canyon: the sound of your voice is reflected by the walls. The greater the distance between you and the barrier, the longer it takes for the reflection to return to you!
Sound Waves travel through different media at different rates:
What conclusion can you make about the nature of a medium
and how quickly
sound will travel?

7. Since sound travels at different speed in different material, sound has to change speed when it passes between two materials. If the wave front hits the boundary at an angle, then one side of the wave will speed up or slow down before the other side, causing the wave to bend. This is, of course, called __________.
Refraction

8. To better understand how sound waves are Diffracted, thing about attending a large concert. As a wave, sound bends around small barriers and radiates out in every direction from gaps in large barriers.

9. RELATED TERMS
Diffusion: When light waves are spread apart or scattered into a lower concentration through certain refractive or reflective materials.
The soft, even blue hue of the entire daytime sky is the result of short wavelength light (blue light) being diffused by the molecules in the Earth’s atmosphere!
Rarefaction : A decrease in density and pressure in a medium, such as air, especially when caused by the passage of a wave, such as a sound wave.
Absorption: When a material “takes in” light waves. Energy is not fully refracted or reflected but actually transferred to the electrons in the matter being struck.
A red shirt selectively absorbs all other visible light wavelengths, yet reflects the “red” wavelengths of the spectrum outward toward our eyes.