BELLRINGER What do you know about different types of waves? How many different types can you think of?

Intro To Waves Chapter 9

WHAT IS A WAVE? Wave: A regular pattern of motion created by vibrations or a disturbance. Waves usually move through matter (anything with mass), but some waves (like light, AKA electromagnetic waves) can move through a vacuum (like outer space)

MOVEMENT of a WAVE Most waves travel through matter (anything with mass), this matter is called a medium: A gas, liquid, or solid substance through which a wave can travel. When a wave travels through a medium, it causes particles to oscillate: A repeating and regular motion (back and forth motion) Waves cause particles to “oscillate” across a certain point which is called equilibrium: defined as the resting position of the particle before the disturbance. Periodic waves: Waves that move at constant speed and oscillate regularly. http://www.showme.com/sh/?h=vkci1lQ https://www.youtube.com/watch?v=7yPTa8qi5X8

WAVES TRANSFER ENERGY NOT MATTER: WHEN YOU SEE A WAVE MOVE THROUGH A SUBSTANCE, YOU ARE SEEING ENERGY MOVE THROUGH THE MEDIUM, A wave does NOT transfer matter. Instead, it causes particles in matter to move up and down (or back and forth). Since these particles always return to their original position, or “Equilibrium” there is technically no “NET” movement, Let me explain.

MECHANICAL WAVES: https://www.youtube.com/watch?v=yd- G6KYwzvA https://www.youtube.com/watch?v=GkNJ vZINSEY As you saw in the videos, there are two main types of mechanical waves, transverse and longitudinal. Transverse waves: Particles move up and down (like ocean waves) Longitudinal Wave: particles move back and forth (like sound waves)

MECHANICAL WAVES “NOTES” Mechanical waves: waves produced by a mechanical movement or vibrations (sound waves, seismic waves during earthquakes, ocean waves) REQUIRE MEDIUM (MOVE THROUGH MATTER)- they cannot travel through a vacuum (outer space) Transfer energy through collisions of particles, once a particle is disturbed it bumps into another one, which bumps into a third particle and so on. https://www.youtube.com/watch?v=wvJAgrUBF4w

ELECTROMAGNETIC WAVES “NOTES” Electromagnetic waves (EM): created by oscillations of electric and magnetic fields Carry electromagnetic energy DO NOT REQUIRE MEDIUM- can travel through outer space RADIANT energy like light, UV, Infrared, radio waves ect. https://www.youtube.com/watch?v=xZ6XUk7QLbU

REVIEW QUESTION What is a wave? The transfer of matter from one location to another A regular patter of motion created by a vibration or disturbance An irregular pattern of motion created by a vibrating object An irregular movement of energy across a vacuum

REVIEW QUESTION What is an oscillation? A regular motion that occurs only once A regular and repeating motion And irregular motion that occurs only once An irregular repeating motion

REVIEW QUESTION A PERIODIC WAVE: Travels at a constant speed Travels with regular oscillations Travels for only a short period of time Both A and B

REVIEW QUESTION WHAT ARE THE DIFFERENCES BETWEEN MECHANICAL WAVES AND ELECTROMAGNETIC WAVES? ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________

PART 2: TYPES OF WAVES Remember that there are two main classifications of waves: Mechanical vs. Electromagnetic waves Mechanical waves are created by a vibrating object or a disturbance (like a rock hitting the surface of a calm lake) Electromagnetic Waves are created by oscillations (review your definitions) of electric and magnetic fields. (like light, radio waves, microwaves, infrared & ultraviolet waves)

Mechanical Waves: 3 Main Classifications of Mechanical waves: Transverse Waves: particles of the medium move perpendicular (90 degrees) to the direction of the wave. (up-and-down when the wave moves left or right) https://www.youtube.com/watch?v=Q6kFhzMa7-w Longitudinal: Particles oscillate parallel (in the same direction) as the wave itself. Sound waves, Pressure waves after a big explosion.

Mechanical Waves Surface (AKA Orbital) waves: A combination of the transverse+longitudinal Usually travel along the surface of a medium (like ocean waves or Seismic waves during an earthquake) Particles oscillate both perpendicular and parallel to the motion of the wave, this combination results in a circular motion.

BELLRINGER: What is the basic difference between a longitudinal and a transverse wave?

Review Questions: How do particles oscillate in a transverse wave? Perpendicular to the motion of the wave Parallel to the motion of the wave In a circular motion Diagonally to the motion of the wave

Review Questions: How do particles oscillate in a Longitudinal wave? Perpendicular to the motion of the wave Parallel to the motion of the wave In a circular motion Diagonally to the motion of the wave

Review Questions: How do particles oscillate in an Orbital (AKA surface) wave? Perpendicular to the motion of the wave Parallel to the motion of the wave In a circular motion Diagonally to the motion of the wave

What type of waves only travel along the surface of a medium? Review Questions: What type of waves only travel along the surface of a medium? Transverse Waves Logitudinal Waves Surface Waves Top Waves

Review Questions: How is a surface wave similar to a transverse wave AND longitudinal wave? How is it Different? _________________________________ _________________________________ _________________________________ _________________________________

PART 3: WAVE PROPERTIES (GRAPHING WAVES) The easiest way to understand the properties of waves is to draw their graph, Cut out page numbered 27 in your waves packet as instructed and glue it to you notebook.

Graphing Waves X-axis (horizontal) = length of time Y-axis (vertical) = measure of height X-axis at y = 0 is defined as EQUILBRIUM (review your vocab)

AMPLITUDE: The Height of a wave Measured from equilibrium to the top of the peak (or CREST), not from trough to crest. Related to the energy of the wave, the higher the amplitude, the greater the energy carried by the wave.

WAVELENGTH ( ) The Length of one Wave Cycle Wave Cycle: one complete path of a wave. The distance from Crest to Crest or Trough to Trough on consecutive waves. Measured in meters

Period The amount of time it takes for one full wavelength to pass by a specific point (Wave Cycle). Periodic waves have a Period that doesn’t change.

FREQUENCY Equals 1/PERIOD Defined as the Number of Waves to pass by a specific point in a Specific amount of time Normally measured in Hertz (Hz), or wave cycle per second

Review video https://www.youtube.com/watch?v=ke7RUj3IJZs

REVIEW QUESTIONS What is a Wavelenght? The length of one wave cycle The time it takes to complete one wave cycle The height of a wave The rate at which a wave moves across space or through matter.

REVIEW QUESTIONS What is Amplitude? The length of one wave cycle The number of wave cycles a wave completes in one second The time it takes to complete one wave cycle The height of a wave

REVIEW QUESTIONS If a waves completes 2 wave cycles in 1 second, what is the frequency of the wave? 1Hz 2Hz 4 Hz ½ Hz

REVIEW QUESTIONS: label wavelength, amplitude, and frequency below

Waves Part 4: Transverse Waves A transverse wave is a wave that causes the particles of the medium to oscillate perpendicular to the motion of the wave Meaning if the wave moves left or right, the particles move up and down!!

EXAMPLES OF TRANSVERSE WAVES A person DISTURBS (or shakes) a rope up and down, this type of transverse wave is mechanical. Electromagnetic (EM) waves are similar to transverse waves, because the electric and magnetic fields oscillate perpendicular to the motion of the wave (that’s why its called electromagnetics) Light, Radio waves, Ultraviolet ect.

Review of Anatomy of a Transverse Wave X-axis can measure time or distance, if it measures time you can determine the frequency of the wave. If it measures distance you can determine the wavelength.

Review of Anatomy of a Transverse Wave Up-and-down movement of the wave represents how the PARTICLES move (oscillation) but the wave is actually moving left or right. As a wave gets closer, particles in the medium move upward until they reach the CREST (high point). As a wave moves away, particles move down, pass equilibrium, and reach the TROUGH (Low point) Then they return to equilibrium

Review of Anatomy of a Transverse Wave CHECK YOUR NOTES!!!: Distance from Equilibrium to crest/trough is called __________. Distance from crest to crest from one wave to the next is called _________. (hint: length of one wave cycle) The NUMBER of wave cycles completed in one SECOND is called _________.

REVIEW QUESTIONS How do particles move in relation to the motion of a transverse wave, as the wave passes through a medium? Perpendicular to the motion of the wave Parallel to the motion of the wave In a circular motion Do not move in the medium

REVIEW QUESTIONS What is the max displacement of a transverse wave called (High Point)? Trough Crest Wavelength frequency

REVIEW QUESTIONS What is the wavelength of a transverse wave? Distance from crest to crest Distance from trough to trough Distance from one point on the wave to the same point on the next wave All of the above

Why are EM waves considered to be transverse waves? Distance from Why are EM waves considered to be transverse waves? ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________

Waves Part 5: Longitudinal Waves Waves that cause particles to move or oscillate parallel to the motion of the wave. They oscillate left and right as the wave moves left or right.

Examples of Longitudinal Waves Pushing the two ends of a slinky together (or moving one end left and right), causing areas of the slinky to be compressed and then spread out Sound is a Longitudinal Wave The blast wave from a bomb is also longitudinal

ANATOMY of a LONGITUDINAL WAVE As a longitudinal wave moves toward an area of a medium (let’s say a slinky), it causes particles in the area to collide. Particles are pressed together in the area, which is called compression or condensation As the wave moves away, the particles stop colliding and spread out. The area where particles are separated is called rarefaction

ANATOMY of a LONGITUDINAL WAVE COMPRESSIONS of longitudinal waves are like CRESTS of transverse waves. RAREFACTIONS are like TROUGHS The Wavelength of a longitudinal wave however, is the distance between two consecutive compressions, or two consecutive rarefactions What does consecutive mean? REMEMBER THE WAVELENGTH IS ALSO THE LENGTH OF ONE WAVE CYCLE, so longitudinal waves also have FREQUENCY

REVIEW QUESTIONS As a longitudinal wave passes through a medium, it causes particles to be pressed together. We call these areas: Compressions Rarefactions Pressure Points High Points

REVIEW QUESTIONS The distance from one compression to the next compression is: The Frequency The Amplitude The Wavelength The Speed of the Wave

REVIEW QUESTIONS Compression is like a crest, and rarefaction is like a: Frequency Half the Wavelength Amplitude Trough

REVIEW QUESTIONS Compare the motion of longitudinal waves to the oscillation of the particles in the medium: _____________________________________ _____________________________________ _____________________________________ _____________________________________ _____________________________________