youtube/watch?v=yVkdfJ9PkRQ (Pendulum)

http://www.youtube.com/watch?v=yVkdfJ9PkRQ (Pendulum)

Waves • Most information reaches us as a form of wave. • Light (electromagnetic), sound, radio/television (electromagnetic) • When energy is transferred by a wave from a vibrating source to a receiver, there is no transfer of matter between the two points. • When you cause a ripple in a pond, the wave disturbance moves, not the water; when the ripple passes,the water is in the same spot as it was prior to the disturbance. • The energy transferred from a vibrating source to a receiver is carried by a disturbance in a medium. • When you speak, the air molecules don’t move away from you like a wind; they simply pass on the disturbance.

Great Sound demos on ‘Sound’ disc!!!!! http://www.youtube.com/watch?v=44kdfyN9ws4&NR=1 (water balloon & ping pong ball)

Vibrations and Waves • A wave is a disturbance that carries energy thru matter or space. • A vibration provides the energy for waves - the bigger the vibration, the bigger the wave. • A vibration cannot exist in one instant, but needs time to move to and fro. • A wiggle in time • As waves carry energy along, they spread that energy over a large area - the farther away you are from the vibration, the less you are affected by it. • Ex:: Homes near an epicenter (source of vibration) of an Earthquake, versus far away • The farther you are from a light source, the dimmer the light that reaches you.

Vibrations and Waves • Waves that move thru space are called electromagnetic waves- their energy is carried thru changing electric and magnetic waves. • Ex: Light and heat travel from the sun thru space

Vibrations and Waves • All other waves are mechanical waves, which must travel thru some form of matter, called a medium, in order to move their energy from one location to another. • Ex: Earthquakes - energy moves thru the ground • NOTE: The wave moves, but NOT THE MEDIUM!!!!!!!! • There are three main categories of mechanical waves, but all three share some important characteristics.

Transverse Waves • Whenever the motion of the medium is at right angles to the direction the wave travels, the wave is a transverse wave. • Shaking a rope up and down - rope moves at right angles to the direction of the wave (along length of the rope). • Waves caused by the stretched strings of musical instruments are transverse. • iPhone in a guitar! • http://m.youtube.com/watch?v=INqfM1kdfUc

Longitudinal Waves • When the particles of the medium move along the direction of the wave, and not at right angles to it, it is a longitudinal waveor compression wave. • The particles are alternately squeezed together, compressions and pulled apart, rarefactions These compressions and rarefactions travel along the medium.

Pyroboard 2d rubens tube • http://www.youtube.com/watch?v=2awbKQ2DLRE • Rubens Tube • http://www.youtube.com/watch?v=hip-4KF6z4o • http://youtu.be/hip-4KF6z4o • http://youtu.be/hip-4KF6z4o • http://youtu.be/gpCquUWqaYw

Surface Waves • A surface waveis a wave that travels along a surface separating two media. • Ex: Ocean wave - Travels along the surface of the water where it meets the air. • As the wave goes by, anything in its path will move up and down as it passes, but also forward and backward, combining to make the object move in a circle. • The entire column of water is moving • Matter is not transported in this type of wave in open water, but as waves approach shore, friction between the shore and water slows the bottom of the wave down and the top falls over it, causing anything that was in the column to move toward the shoreline, like a toppling building. (ESSAY QUESTION!!!!!)

Parts of a Wave • Crests – • High points in a transverse or surface wave • Compressions in a longitudinal wave • Troughs • Low points in transverse or surface waves • Rarefactions in longitudinal waves • The midline is a straight line drawn thru the crests and troughs that represents the middle of the wave…this is equilibrium. www.bbc.co.uk

Parts of a Wave • The amplitude of a wave is the distance from the midline to the crest (or to the trough) of the wave. Thus, the amplitude is the maximum displacement from equilibrium. • In a longitudinal wave, it is the distance from the rest area to the area of greatest compression or rarefaction. • The greater the energy of a wave, the greater it’s amplitude. Amplitude.pngwww.gwenio.com

Parts of a Wave • Any motion that occurs over and over at regular intervals is called periodic motion. • The period is the time required for one cycle – from start and back again – to complete. • Ex: Pendulum swing from the time you let it go until it comes back to your hand. • Ex: From the crest of one wave to the crest of the next. Period science-class.net

Parts of a Wave • Frequency is how many waves pass by in a set period of time, ….measured in cycles per second or hertz (Hz)- Heinrich Hertz demonstrated radio waves in 1886. • The frequency of a wave is equal to the frequency of the vibration that causes it. • One vibration per second is 1 Hz; 2 is 2 Hz. • Higher frequencies are measured in kilohertz (kHz) or megahertz (MHz)……AM radio waves are broadcast in kilohertz and FM are broadcast in megahertz. • A station transmitting at 101 MHz on the FM dial, broadcasts radio waves with a frequency of 101 000 000 Hz. This is the frequency at which the electrons must vibrate in the antenna of the radio station’s transmitting tower. If your car stereo is set at 101FM, then its antenna is also vibrating at 101 000 000 Hz and picks up the signal.

Parts of a Wave • If you look at the definitions, period and frequency are the inverse of one another…… • The longer the period, the smaller the wave frequency. • The greater the frequency, the shorter the period must be. • Frequency = 1/period…….Period = 1/frequency • If an object’s frequency is 2 Hz (2 vibrations per sec), its period (time needed to complete one vibration) is 1/2 sec • If an object’s frequency is 3 Hz, its period is 1/3 sec

Parts of a Wave • The wavelength of a wave is the distance from the top of one crest to the top of the next (or between any successive, identical parts of a wave). • Wavelengths on a beach are measured in meters; in a pond in cm, and of light in micrometers. • Wave speedcan be found by: • Wave speed = wavelength (λ) / period (T) how long the wave is / how long it take to go by ORWave speed = wavelength (λ) x frequency (f) how long the wave is * how many in a second • Increasing the frequency of a wave will decrease it’s wavelength.

Wave speed (v) = wavelength (λ) / period (T) how long the wave is / how long it take to go by ORWave speed (v) = wavelength (λ) x frequency (f) how long the wave is / how many in a second • A wave on a rope has a wavelength of 2.0 m and a frequency of 2.0 Hz. What is the speed of the wave? • A motorboat is tied to a dock with its motor running. The spinning propeller makes a surface wave in the water with a frequency of 4 Hz and a wavelength of 0.1m. What is the speed of the wave? • What is the speed of a wave in a spring if it has a wavelength of 10cm and a period of 0.2s? • What is the wavelength of an earthquake wave if it has a speed of 5km/s and a frequency of 10 Hz?

Wave speed (v) = wavelength (λ) / period (T) how long the wave is / how long it take to go by ORWave speed (v) = wavelength (λ) x frequency (f) how long the wave is / how many in a second • A wave on a rope has a wavelength of 2.0 m and a frequency of 2.0 Hz. What is the speed of the wave? v = ____ λ = 2.0 m f = 2.0 Hz V = 2.0m x 2.0 1/s = 4 m/s

Wave speed (v) = wavelength (λ) / period (T) how long the wave is / how long it take to go by ORWave speed (v) = wavelength (λ) x frequency (f) how long the wave is / how many in a second • A motorboat is tied to a dock with its motor running. The spinning propeller makes a surface wave in the water with a frequency of 4 Hz and a wavelength of 0.1m. What is the speed of the wave? v = ____ λ = 0.1 m f = 4 Hz V = 0.1m x 4 1/s = .4m/s

Wave speed (v) = wavelength (λ) / period (T) how long the wave is / how long it take to go by ORWave speed (v) = wavelength (λ) x frequency (f) how long the wave is / how many in a second • What is the speed of a wave in a spring if it has a wavelength of 10cm and a period of 0.2s? v = ___ λ = 10cm T= 0.2 s V = 10cm / .2s = 50 cm/s

Wave speed (v) = wavelength (λ) / period (T) how long the wave is / how long it take to go by ORWave speed (v) = wavelength (λ) x frequency (f) how long the wave is / how many in a second • What is the wavelength of an earthquake wave if it has a speed of 5km/s and a frequency of 10 Hz? v = 5 km/s λ = ____ f = 10 Hz λ = v / f = 5 km/s / 10 1/s = .5 km

Vibrations of a Pendulum • A stone hung from a string is a simple pendulum. • Pendulums swing to and fro with such regularity that they have been used to control the motion of clocks. • The time it takes a pendulum to swing thru its angle is its period. • A period depends on the length of the pendulum and the acceleration due to gravity. The mass of the pendulum does not affect it. • A long pendulum has a longer period than a short pendulum - it swings to and fro more slowly. • When walking, our legs swing with the help of gravity, much like a pendulum; & like a pendulum, a person with longer legs often has a slower stride (giraffes & horses vs hamsters and dachshunds)

Mechanical Waves • The speed of the wave depends on the medium thru which it travels. • Sound waves travel at 330m/s to 350 m/s in air and about 4 times that in water. • Waves travel fastest thru solids, and slowest thru gases….why? • All things being equal, the distance between molecules has some effect, but if that was it, then all solids would transmit waves well – and they do not! • Elasticity! Remember, the molecules need to vibrate back and forth so if they are unable to spring back, then they cannot carry the impulse well. Ex: play dough versus steel • Temperature can affect waves - how? • Warmer temps equal faster moving particles so they pass on energy more quickly…..cooler temps equal slow moving particles.

32 out of sync metronomes… • https://www.youtube.com/watch?v=kqFc4wriBvE&feature=youtube_gdata_player • Or • http://youtu.be/kqFc4wriBvE

Wave Interactions • A reflection occurs when a wave bounce back when it meets an obstacle (wall), or a boundary between different media (move from air to water). • The speed and frequency of the wave does not change, but it can be flipped upside down. • Yell into a cave and your words will travel until they hit a wall, and then they bounce back at you as an echo. • Other than objects like lamps that emit their own light, everything you see is reflecting light waves. • Light waves striking the surfaces of animals, houses, etc, reflect back to you, allowing you to see them and identify colors. (If its pitch black, you can’t see anything cuz there’s no light to be reflected off of the objects.)

9GAG - Physics is phun.9gag.com

Wave Interactions • Refraction is the bending of waves when they pass from one medium to another, or when the density of a medium changes. • Occurs when one side of a wave moves more slowly than the other. • Studying refraction of underground earthquake waves have given us what we know about the Earth’s interior. • Refraction explains why sound waves travel so much more clearly across a body of water at night - the cool air above the water refracts the sound waves in a downward arc toward the other side of the lake.…..when the air was warmer during the day, the same waves would have refracting upward and away from someone on the other side of the lake. • Not being able to hear as well across a camp fire

Wave Interactions • Diffraction is a bending of a wave as it moves around an obstacle or through a narrow opening. • The larger the wavelength compared to the obstacle or opening, the greater the diffraction. • AM radio wavelengths are much larger than FM • When an AM radio wave reaches an obstacle, it bends a great deal – spreading the signal out over a large width of area. • FM radio waves can be blocked and lost as you go down into a low point in a road, or around a large hill. • The shorter wavelengths give you more definition and clarity • FM stations are clearer and crisper • Can see eyelashes on an ultrasound

This photo sequence taken in Veszprem, Hungary As the sun sets toward the horizon, the light has to travel a longer distance to us and is scattered more. The shorter wavelengths (blues and greens) aren’t as able to get around the particles in their way and are scattered more, and the reds and oranges are able to get around the particles in the way more easily and are the ones that mostly get to us. - Taken in Veszprem, Hungary

Wave Interactions • An interference patternoccurs when more than one vibration is acting in a place at one time, causing 2 or more waves to overlap and combine. • Within a interference pattern, the wave effects may be increased, decreased or neutralized. • Adding the amplitudes of the waves together, gives you the resulting wave. http://youtu.be/PCYv0_qPk-4 http://youtu.be/q74qF6I1uew

Wave Interactions • Constructive Interference: When the crest of one wave overlaps the crest of another wave, their individual effects add together, resulting in a wave of increased amplitude. • Destructive Interference: When the crest of a wave overlaps the trough of another wave, the individual effects are reduced - the high part of one wave fills in the low part of the other. • Can result in neutralization of the wave if the amplitudes are the same size.

Interference When the crest of one wave overlaps the crest of the other, the wave are in phase with each other and amplify. When the crest of one wave overlaps the trough of the other, the waves are out of phase with each other and diminish or cancel out.

Wave Interactions • In a concert hall, you have many sources of sound being directed out toward the audience. • Once the sound leaves the instruments, it may travel directly to the listener, but also moves out across the entire hall and reflects from surfaces around the room. • If a reflected wave interferes with an original wave, they can cancel out and cause ‘dead spots’ where the volume is greatly reduced. • To avoid this, • theatres are designed with sound-absorbing tiles and reflecting panels to control where the sound goes, ensuring it does not double back on itself but instead moves toward the audience.

Wave Interactions http://youtu.be/q2AynYYMskA • Noise-cancellation technology uses interference to cancel out unwanted noise. • Receivers in headsets analyze the amplitude and frequency of unwanted sounds, and then a tiny speaker emits a wave at the same frequency but out of phase so that the two meet and cancel out in destructive interference. • This type of technology distinguishes between sounds you do not want and sounds you do so that you can hear your coworker talking to you over the sound of the jet engine.

Standing Waves • By shaking a rope just right, it is possible to cause the incident (original) wave and the reflected wave to form a standing wave……in a standing wave, the nodes are points along the rope that remain stationary. • The positions on a standing wave with the largest amplitudes are the antinodes. • Antinodes occur halfway between the nodes • Standing waves are the result of interference…. • When two waves of equal amplitude and wavelength pass thru each other in opposite directions, the waves are always out of phase at the nodes. • Standing waves can be produced in either longitudinal or transverse waves.

Standing Waves Incident Wave Antinode Node Reflected Wave

Standing Wave Videos – Rubens Tube http://www.youtube.com/watch?v=ynqzeIYA7Iw http://www.youtube.com/watch?v=gpCquUWqaYw Physics Girl – Singing Plates: https://www.youtube.com/watch?v=wYoxOJDrZzw or http://youtu.be/wYoxOJDrZzw

Sound Waves • Sound waves are mechanical waves and therefore follow the same behaviors, with a few additional terms specific to sound. • Intensity is the rate at which a wave’s energy flows through a given area. • Depends on amplitude and the distance from the source. • Measured in decibels (dB) which is a unit developed to compare different sounds. • The greater the decibel level, the greater the intensity and the greater the possible damage your ear may receive from that sound. (chart on p. 515) • Loudness is a physical response to intensity. • Depends on intensity but also the health of your ears and how your brain interprets information in the sound waves.

Wave Characteristics https://www.youtube.com/watch?v=dbeK1fg1Rew First half on parts of wave……last half on pitch

Sound Waves • Remember, frequency depends on the speed of the vibrating source. • Pitch is the frequency of a sound as you perceive it. • Affected by the wave’s frequency but again, also on age, health, etc. • The higher the frequency of a wave, the higher it’s pitch. • Musical Instruments produce standing waves in the tubing (trumpet, oboe, pipes), along the strings (piano, violin) or across the vibrating surfaces (drums) that makes them up – Diff in a bass drum and snare? • the longer the tubing, string or larger surface area, the longer the wavelength of that standing wave that can be created the lower the frequency = lower pitch. • Shorter tubing (string, surface area) allows for only short standing waves = higher frequencies and therefore higher pitch.

http://science360.gov/obj/video/7f361151-7757-4083-86f4-81899df65bfa/innovation-nation-sound-bulletshttp://science360.gov/obj/video/7f361151-7757-4083-86f4-81899df65bfa/innovation-nation-sound-bullets

Music • Most musical instruments change the frequency of standing waves to change their pitch. • Resonance is the response of a standing wave to another wave of the same frequency. • Can produce a dramatic increase in amplitude. • Soundboard in a piano is a board that resonates or vibrates in response to the vibrating strings, increasing their amplitude. • Acoustic guitars use a soundboard (the wooden front and back of the guitar) and sound box (hollow cavity) - vibrations from the strings resonate the soundboard and resonate the air inside the sound box, changing amplitude depending on how those frequencies align.

http://www.youtube.com/watch?v=uENITui5_jU&feature=youtube_gdata_playerhttp://www.youtube.com/watch?v=uENITui5_jU&feature=youtube_gdata_player Camera trick: Camera is set to 24 Frames per second – When sound frequency is same, appears still; When sound frequency is at 25Hz, appears to move slowly forward; When sound frequency is at 23Hz, appears to move slowly forward

Sound Waves • Most people hear sounds between 20 Hz and 20,000 Hz though age affects this a great deal. • As you age you lose the ‘ends’ of that spectrum, so you can hear much higher and lower sounds than your parents can. • Ultrasound is sound higher than most people hear and infrasound is sound at lower frequencies. • Sonar (sound navigation and ranging) bounces sound off of objects in water, and then uses the speed of sound in water and the time it takes for the echo to return to determine the distance to the object and create a 3D map of it. • Ultrasound imagingis used in the same way on much smaller objects, i.e. human organs, fetus in the womb, etc.

Sound Waves • A change in frequency relative to motion of the source or receiver or both is called the Doppler effect. • The greater the speed of the source (or receiver) the greater the Doppler effect. • The wave crests in front of a moving source of light or sound are closer together than those behind it, so the receiver would experience a higher frequency if he is in front of the source. • Changing pitch of a car horn as it passes by - as it approaches, its pitch is higher because its sound wave crests are reaching you more frequently; as it passes and moves away, the pitch drops cuz the waves encounter you less frequently. • http://videos.howstuffworks.com/discovery/27963-assignment-discovery-doppler-effect-video.htm http://www.youtube.com/watch?v=LIvVzJ6KZpk

The Doppler Effect • Light waves also experience the Doppler effect….as a light source approaches, there is an increase in frequency and as it recedes, there is a decrease in frequency • An increase in light frequency is called a blue shift, as the increase is toward the high-frequency, or blue, end of the color spectrum. • A decrease in frequency is called a red shift, referring to the low-frequency, or red, end of the color spectrum. • When scientists look at the universe they see a trend toward a red shift, which indicates that the expansion of the universe is slowing, supporting the Big Bang theory.

Sound Waves • When the speed of the source is the same as the speed of the waves it produces, a ‘wave barrier’is produced. • When a wave barrier is produced, the crests keep piling up in front of the source; in order for the source to pass this barrier and go faster, it must exert a great deal of energy. • When aircraft fly at the speed of sound, a barrier of compressed air is produced in front of the plane. Additional thrust is required to burst through. • The sudden increase in pressure can cause the water vapor in the air to condense into visible water droplets or clouds. The Prandtl–Glauert Singularity – Amazing Jet Plane Shock Collar ...www.kuriositas.com Ares I-X Launch Image Gallerywww.universetoday.com

Shock Waves https://www.youtube.com/watch?v=gWGLAAYdbbc&feature=youtube_gdata_player • A boat speeding thruwater faster than the waves it is producing, creates a 2 dimensional shock wave. An aircraft flying faster than the speed of sound (supersonic) produces a 3 dimensional shock wave. • A shock wave is produced by overlapping spheres that build up. The conical shock wave spreads until it reaches the ground. • A sonic boom is the sharp crack of noise heard when the conical shock wave reachesthe listeners on the ground.

youtube/watch?v=yVkdfJ9PkRQ (Pendulum)