May 15, 2009 Is there sound in space? Why or why not? Get out your computer lab activity packet!

Goals To identify parts of waves To calculate values associated with waves To distinguish between types of waves

Q: What is a wave? Disturbance that travels through a medium (substance)

Q: What is a wave? When a wave isn’t traveling, it is considered to be in equilibrium position Imagine a stretched out slinky just sitting on a desk- that’s equilibrium

Q: What is a wave? Once a particle moves at the front, the energy of that particle will travel throughout the slinky to the other end. That creates a wave!

Q: What is a wave? Waves transfer energy, not particles This explains why boats sitting in the middle of the ocean can just sit in one spot, and don’t travel with waves

Q: What are some types of waves? Transverse Particles move perpendicular to the direction of energy transfer Particles move up and down, but energy is transferred left to right. These are the waves we draw/imagine when we hear the word.

Q: What are some types of waves? Longitudinal Particles move parallel to the direction of energy transfer Particles move left and right, energy transferred left and right.

Q: What are some types of waves? Electromagnetic Waves Can transfer energy in a vacuum (SPACE!) Ex: Light waves Mechanical Waves Cannot transfer energy in a vacuum Ex: sound

Q: What are some parts of waves? Transverse Crest (High point) Trough (Low point)

Q: What are some parts of waves? Longitudinal Compression (High pressure) Rarefaction (Low pressure)

Q: What are some parts of waves? Wavelength: length of one cycle Transverse: 1 trough and 1 crest Longitudinal: 1 compression and 1 rarefaction Ex. Distance from one crest to the next Distance from one trough to the next Distance from one compression to the next

Q: What are some parts of waves? Units: same as those for DISTANCE Meters Usually with a prefix NANO 1 m = 109 nm

Q: What are some parts of waves? Amplitude Displacement (movement) of particles from equilibrium (rest) position Most of the time considered to be from rest to crest or rest to trough Harder to measure in longitudinal waves

Q: What are some parts of waves? Amplitude, cont Units: Same as DISTANCE (some form of meters, usually with prefix- see wavelength section) Increased amplitude means louder sound.

Q: What do you mean when you talk about the frequency and period of a wave? Amount of wave cycles that pass in a certain amount of time NOT the same as speed of a wave!

Q: What do you mean when you talk about the frequency and period of a wave? Frequency, cont Units: Hertz, Hz (cycles per second) Increased frequency means higher “pitch”

May 18, 2009 What is the difference between frequency and speed? If you increase the period, the frequency will ____________.

Q: What do you mean when you talk about the frequency and period of a wave? The amount of time it takes for one complete cycle Units: same as for time (seconds, hours, minutes, years, etc)

Relationship between the two Q: What do you mean when you talk about the frequency and period of a wave? Relationship between the two As you increase the frequency, the period will decrease Inversely related

Q: What do you mean when you talk about the frequency and period of a wave? Equation: Units: Frequency is hertz (Hz) Period in seconds

PRACTICE PROBLEMS Frieda the fly flaps its wings back and forth 121 times each second. The period of the wing flapping is ____.

PRACTICE PROBLEMS 2. The period of the sound wave produced by a 440 Hertz tuning fork is _________.

PRACTICE PROBLEMS 3. A tennis coach paces back and forth along the sideline 10 times in 2 minutes. The frequency of her pacing is ______.

PRACTICE PROBLEMS 4. Olive Udadi accompanies her father to the park for an afternoon of fun. While there, she hops on the swing and begins a motion characterized by a complete back-and-forth cycle every 2 sec. The frequency of swing is _____. The period of swing is ______.

Q: What is the relationship between speed, frequency, and wavelength? Speed is not dependent on wavelength or frequency Speed IS dependent on the medium of travel Waves travel fastest through solids and slowest through gases Think of the closeness of particles/ease of energy transfer!

Q: What is the relationship between speed, frequency, and wavelength? As the wavelength increases: Waves spread out, so frequency decreases Wavelength and frequency are INVERSELY related

Q: What is the relationship between speed, frequency, and wavelength? WAVE Equation: Units: frequency in hertz (Hz) wavelength can be any type of distance units velocity is in distance units over seconds

PRACTICE PROBLEMS 1. Mac and Tosh stand 8 meters apart and demonstrate the motion of a transverse wave on a snakey. The wave can be described as having a vertical distance of 32 cm from a trough to a crest, a frequency of 2.4 Hz, and a horizontal distance of 48 cm from a crest to the nearest trough. Determine the amplitude, period, and wavelength and speed of such a wave.

PRACTICE PROBLEMS 2. Ocean waves are observed to travel along the water surface during a developing storm. A Coast Guard weather station observes that there is a vertical distance from high point to low point of 4.6 meters and a horizontal distance of 8.6 meters between adjacent crests. The waves splash into the station once every 6.2 seconds. Determine the frequency and the speed of these waves.