1. Harmonic Motion and Waves 3.3.2015Arsenie

2. Harmonic motion is motion that has a pattern or repetition. This type of motion is called oscillation. Harmonic motion is motion that has a pattern or repetition. This type of motion is called oscillation. Things that oscillate have a cycle. We measure several things about a cycle.

4. Period (T) is the time it takes for one cycle to complete. It is measured in seconds. Period (T) is the time it takes for one cycle to complete. It is measured in seconds. Frequency ( f ) is the number of cycles that occur in one second. It is measured in Hertz (Hz). 1 cycle per second = 1 Hz. Frequency ( f ) is the number of cycles that occur in one second. It is measured in Hertz (Hz). 1 cycle per second = 1 Hz. 1 million cycles per second = 1,000,000 Hz = 1MHz. 1 million cycles per second = 1,000,000 Hz = 1MHz. Amplitude (A) is the size of the cycle away from its center of equilibrium/rest. We measurethe distance in meters or an angle in degrees. Amplitude (A) is the size of the cycle away from its center of equilibrium/rest. We measurethe distance in meters or an angle in degrees.

5. Amplitude Amplitude measures the “greatness” of a wave, or the maximum height from the center. Units can be in m or the angle. Amplitude measures the “greatness” of a wave, or the maximum height from the center. Units can be in m or the angle. Example: a pendulum’s amplitude of 20 cm, or 30 °

7. A wave is an oscillation that travels. A wave is an oscillation that travels.

8. Waves carry useful information and energy. Waves carry useful information and energy. Waves are all around us: Waves are all around us: light from the stoplight light from the stoplight ripples in a puddle ripples in a puddle electricity flowing in wires electricity flowing in wires radio and television and cell phone transmissions radio and television and cell phone transmissions

9. Anytime you see a vibration that moves... Anytime you see a vibration that moves... Anything that makes or responds to sound... Anything that makes or responds to sound... Anything that makes or responds to light... Anything that makes or responds to light... Anything that transmits information through the air (or space) without wires... Anything that transmits information through the air (or space) without wires... cell phones, radio, television cell phones, radio, television Anything that allows you to “see through” objects... Anything that allows you to “see through” objects... ultrasound, CAT scans, MRI scans, and X rays ultrasound, CAT scans, MRI scans, and X rays

10. Waves have cycles, frequency, and amplitude, because they are oscillations. Waves have cycles, frequency, and amplitude, because they are oscillations. The frequency of a wave tells how often each point oscillates. The amplitude of a wave is the maximum movement from equilibrium.

11. The wavelength ( λ ) of a wave is the length of one complete cycle. It is measured in meters. Crest Trough

12. The speed of a wave equals the frequency times the wavelength. v = f Frequency (Hz) Wavelength (m) Speed (m/sec)

13. A very important and confusing note: The speed of a wave will not change if you increase the period. The reason is this: The speed of a wave will not change if you increase the period. The reason is this: if you increase the time, you are actually stretching the wave out. You see time as a larger number, but: if you increase the time, you are actually stretching the wave out. You see time as a larger number, but: This will decrease the frequency proportionally (less of it will happen in 1 second). This will decrease the frequency proportionally (less of it will happen in 1 second). That also means the wavelength had to increase proportionally (stretch out farther). That also means the wavelength had to increase proportionally (stretch out farther).  So if the period is increased,  the frequency is decreased by the same amount,  and the wavelength is increased by the same amount,  which means that the speed ( f x λ ) will STAY THE SAME number as it was before.  EVERYTHING IS PROPORTIONAL

14. WAVE WAVE SPEED IS ONLY DEPENDENT ON THE MEDIUM IT IS TRAVELING THROUGH. This This means that whatever kind of wave it is, it will indefinitely travel at the same speed, speed, no matter the change in frequency, wavelength, period, etc. It It will only change speed when it passes through a different medium (water, air, oil, pudding, applesauce, etc). When When you tighten a guitar string, you change the tension. This counts as changing the medium.

15. Transverse waves: these oscillate perpendicularly to the direction of the wave. The wave moves left to right, but the oscillation is up and down. The wave moves left to right, but the oscillation is up and down. Water, light, electricity Water, light, electricity Longitudinal Waves These oscillate parallel to the wave direction. These oscillate parallel to the wave direction. springs stretching and compressing (slinkies), sound springs stretching and compressing (slinkies), sound

16. Wave interactions Wave is absorbed by a material and energy is transferred (lose amplitude)

17. The material a wave interacts with is called a boundary. The material a wave interacts with is called a boundary. The wave approaching a boundary is called the incident wave. The wave approaching a boundary is called the incident wave. The wave sent from a boundary is the reflected wave. The wave sent from a boundary is the reflected wave. A wave that is bent passing through a boundary is called a refracted wave. A wave that is bent passing through a boundary is called a refracted wave. This incident plane wave refracts a circular wave after passing through a convex barrier.

18. Waves add up when they cross each other. Waves add up when they cross each other. Two pulses traveling towards each other combine into a resultant pulse. = Waves will pass each other and keep going… Waves will pass each other and keep going… After they pass…