1. Vibrations and Waves
Wave Interactions

2. Interference
Interference – the combination of two or more waves that exist in the same place at the same time
Waves in the same place combine to produce a single wave
Superposition

3. Interference
Constructive interference – displacement in the same direction
Interference in which individual displacements on the same side of the equilibrium position are added together to form the resultant wave
Crests of waves overlap or troughs of waves overlap
Amplitudes are added

4. Interference

5. Interference
Destructive interference – displacement in the opposite direction
Interference in which individual displacements on opposite sides of the equilibrium position are added to form the resultant wave
Crest of one wave meets the trough of another wave
Essentially, amplitudes are subtracted

6. Interference

7. Interference

8. Interference Interference in light waves create colors
Light separates into different colors
Rainbow effects
Interference in sound waves create beats
Constructive interference produces loud sounds
Destructive interference produces soft sounds
Patterns of constructive and destructive interference alternate loud and soft sounds, producing beats

9. Reflection
Reflection – the bouncing back of a wave as it meets a surface or boundary
At a moveable boundary, the reflected wave looks just like the original wave
At a non-moveable boundary, the reflected wave is turned upside down

10. Reflection

11. Diffraction
Diffraction – the bending of a wave as it passes an edge or an opening
Waves spread out to fill space
Allows us to hear sounds through doors

12. Diffraction

13. Refraction
Refraction – the bending of waves as they pass from one medium to another
All waves are refracted when they change
media
Refraction explains why spoons look broken when part of them is in air and part in water

14. Refraction

15. Standing Waves
Standing wave – a wave pattern that results when two waves of the same frequency, wavelength, and amplitude travel in opposite directions and interfere
Standing waves do not move through the medium
Standing waves cause the medium to vibrate in a loop or in a series of loops

16. Standing Waves
Nodes – a point in a standing wave that always undergoes complete destructive interference and therefore is stationary
areas of no vibration
Antinodes – a point in a standing wave halfway between two nodes, at which the largest amplitude occurs
areas of maximum vibration
Standing waves occur at specific frequencies

17. Standing Waves

18. Standing Waves