1. Chapter 11:Vibrartions and Waves
Section 3: Properties of Waves
Section 4: Vibrations and Waves

2. Section 3: Properties of Waves

3. Wave Motion A wave is the motion of a disturbance.
Ex: Ripples in a pond
A medium is the physical environment through which a disturbance/wave can travel.
Ex: The pond
A mechanical wave is a wave that requires a medium to travel through.
Ex: Sound Waves (electromagnetic waves are NOT material waves because they can travel in space)

4. Wave Types Pulse Wave: a wave that has one pulse.
Periodic Wave: a wave that has continuous pulses.
Sine Wave: describe particles that vibrate with simple harmonic motion.
Simple Harmonic Motion: any single point on the wave vibrates up and down.
Transverse Wave: a wave where the vibrations are perpendicular to the wave motion.
-Ex: Light Waves
-Crest: the highest point above the equilibrium position.
-Trough: the lowest point above the equilibrium position.
-Amplitude: distance from equilibrium to crest or trough.
-Wave length (λ): distance from crest to crest or trough to trough.
Longitudinal Wave: a wave where the vibrations are parallel to the wave motion.
-Ex: Sound Waves
- Areas that are compressed are density and pressure waves.
-Longitudinal Waves can be represented on a waveform (compressed areas are
represented by crests and stretched areas are represented by troughs).

6. Period, Frequency and Wave Speed
Wave Frequency describes the number of waves that pass a given point in a unit of time.
Period of Wave describes the time it takes for a complete wavelength to pass a given point.

8. Equations v= Δx/ Δt v= λ/T f= 1/T v= λ/T = f λ v=f λ v= velocity (m/s)
f= 1/T
v= λ/T = f λ
v=f λ
v= velocity (m/s)
Δt= change in time (s)
Δx= displacement (m)
λ = wavelength (m)
T= period of vibration (s)
f= frequency (Hz)

9. Waves transfer energy -The greater the amplitude the more energy
-The energy transferred is proportional to the square of the amplitude.
- Damping: the amplitude of wave gradually diminishes over time as its energy is dissipated.

10. Section 4: Wave Interactions

11. Wave Interaction -Superposition: The combination of two or more waves.
-The waves Interact to form Interference Pattern

12. Constructive Interference
Constructive Interference: When the resultant wave is larger than the individual displacements.
-The two pulses are traveling towards each other on the same side of the equilibrium position
-Superposition Principle- When two or more waves travel through a medium at the same time, the resultant wave is the sum of the displacements of the individual waves at each point.
-After the pulses pass each other, they have the same shape and are going in the same direction.
-Ex: In a concert, the waves travel in all directions and crash into each other but still maintain their own characteristics.

14. Destructive Interference
Destructive Interference: When the positive and negative displacements are added, the resultant wave is the difference between the pulses.
-The two pulses are traveling towards each other on opposite sides of the equilibrium position
-Complete Destructive Interference- When two pulses coincide and the displacements are added, the resultant wave has a displacement wave of zero.
-After the pulses pass each other, they have the same shape and are going in the same direction.
-Ex: When a compression (particles move together) and a refraction (particles move apart) interfere, there is destructive interference.

16. Reflection -At a free boundary, waves are reflected.
-The reflected pulse is upright and has the same pulse as the incident (original) pulse
-At a fixed boundary, waves are reflected and inverted.
-The displacement is in the opposite direction of the original pulse and the amplitude is the same.

18. Standing Waves
-Standing Wave: A wave pattern that results when two waves of the same frequency, wave length, and amplitude travel in opposite directions and interfere
-The resultant wave pattern appears to be stationary on the string.
-Nodes: Points at which complete destructive interference happen.
-Antinodes: The midway point between two adjacent points at which the largest displacement/amplitude occurs.
-A standing wave with 2 nodes has a wavelength of 2 times the size between the nodes. (Or 2 times the size of the whole string (L), so 2L)
-A standing wave with 3 nodes has a wavelength of 2 times the size between the nodes. (Or 2 times the size of the 1/2 of the string (L), so L)
-A standing wave with 4 nodes has a wavelength of 2 times the size between the nodes. (Or 2 times the size of the 1/3 of the string (L), so 2/3L)