WAVES Repeating movement or disturbance that transfers ENERGY, not stuff’’ thru matter or space.

Mechanical Require a MEDIUM to travel; can be solid, liquid or gas. Examples: SOUND, earthquakes, water waves

DO NOT Require a MEDIUM to travel; can travel thru empty space electromagnetic DO NOT Require a MEDIUM to travel; can travel thru empty space Examples: LIGHT

1. mechanical Transverse (sine) Matter moves up and Examples Seismic Ocean Surface Transverse (sine) Matter moves up and down while energy moves thru Amplitude -measurement of how much energy a wave carries! CREST wavelength baseline trough amplitude

1. mechanical sound longitudinal (compressional) Examples sound longitudinal (compressional) Energy and matter move in the same direction wavelength rarefaction compression

v = f The Math Period: How long it takes for 1 full wave to pass frequency: How many waves pass per second v = f

Behavior of waves Reflection WAVES BOUNCE OFF when hitting a boundary that they cannot go thru Causes waves to change direction EXAMPLES: Viewing yourself in a mirror ECHOS

Behavior of waves Refraction WAVES BEND due a change in speed as the wave changes mediums (moves thru something else) The more bent, the more the change in speed Examples: pencils look bent in a glass Being able to hear around corners

Behavior of waves Diffraction WAVES GO THRU barriers and spread Amount of spreading depends on size of barrier

Hewitt wave intereference WAVE INTERFERENCE Hewitt wave intereference Waves are energy – they can be in the same place at a the same time When two waves occupy the same space they interfere with each other – called SUPERPOSITION

CONSTRUCTIVE When crest meets crest – INCREASES AMPLITUDE or trough meets trough LOUDER sound

DESTRUCTIVE When crest meets trough – DECREASES AMPLITUDE

STANDING WAVES Formed due to interference and reflection Standing waves appear to have parts that are not moving

STANDING WAVES

Practice 14

MORE ON SOUND Vibrating air molecules – no sound in space – not enough air Sound travels fastest in solids, slowest in gases FREQUENCY determines PITCH AMPLITUDE determines VOLUME The speed of sound at room temperature is 341 m/s

THE DOPPLER EFFECT Big Bang Theory Doppler Occurs when the source or observer are moving – apparent change in frequency LOW frequency long wavelength HIGH frequency Small wavelength

RESONANCE Physics Girl Glasses Outrageous Symphony Gallopin Gertie

Reflection – wave bounce off when hitting a boundary Refraction – waves bend, change speed due to changing mediums Doppler apparent change in frequency as the observer or source of sound moves- Resonance – one object makes another object vibrate at its natural frequency Interference – increase or decrease in amplitude of the wave where two or waves meet

PHET Wave on a String file:///C:/Users/Looper/AppData/Local/Temp/wave-on-a-string_en.html

25.3 Wave Motion think! The Sears Tower in Chicago sways back and forth at a frequency of about 0.1 Hz. What is its period of vibration? Answer: The period is

CONCEPTS you need to know… A surfer who wishes to ride a big wave is most interested in the ____ of a wave. A sound wave that has a higher frequency has a wavelength that is SHORTER/LONGER? The frequency of the second hand on a clock is _________. A weight on the end of a spring bobs up and down one complete cycle every 5 seconds. Its period is ________________.

A repeating back-and-forth motion about an equilibrium position is a vibration. WAVE: A disturbance that is transmitted progressively from one place to the next with no actual transport of matter . TRANSFER ENERGY Light and sound are both forms of energy that move through space as waves.

25.2 Wave Description The source of all waves is something that vibrates.

25.2 Wave Description The high points on a wave are called crests. The low points on a wave are called troughs. The term amplitude refers to the distance from the midpoint to the crest (or trough) of the wave. The amplitude is the maximum displacement from equilibrium. The wavelength of a wave is the distance from the top of one crest to the top of the next one.

25.2 Wave Description Frequency The number of vibrations an object makes in a unit of time is an object’s frequency. The frequency specifies the number of back-and-forth vibrations in a given time (usually one second). The unit of frequency is called the hertz (Hz). A frequency of one cycle per second is 1 hertz, two cycles per second is 2 hertz, and so on.

25.2 Wave Description If you know an objects frequency you can calculate it’s PERIOD. The time it takes to do complete cycle. What is the period of a wave that has a wavelength of 0.80 m and is traveling at 2.0 m/s?

Wave Parts Definitions Amplitude—the height of a wave from equilibrium to crest (or trough) Period—the time it takes for one entire wave to pass a point Frequency—the number of waves that pass a given point per time period

25.4 Wave Speed The speed of a wave depends on the medium through which the wave moves. Whatever the medium, the speed, wavelength, and frequency of the wave are related.

Wavelengths must be measured from crest to crest. 25.4 Wave Speed If the wavelength is 1 meter, and one wavelength per second passes the pole, then the speed of the wave is 1 m/s. Wavelengths must be measured from crest to crest.

25.4 Wave Speed If the wavelength is 3 meters and if two crests pass a stationary point each second, then 3 meters × 2 waves pass by in 1 second. The waves therefore move at 6 meters per second. v = f where v is wave speed,  is wavelength, and f is wave frequency.

25.4 Wave Speed In air, the product of wavelength and frequency is the same for every frequency of sound. Long wavelengths have low frequencies, and short wavelengths have high frequencies.

3 Types of Wave Motion Longitudinal and Transverse WaveMotion Compressional (Longitudinal)

25.5 Types of Waves Suppose you create a wave along a rope by shaking the free end up and down. The motion of the rope is at right angles to the direction in which the wave is moving. Whenever the motion of the medium is at right angles to the direction in which a wave travels, the wave is a transverse wave.

25.6 Longitudinal Waves Sometimes the particles of the medium move back and forth in the same direction in which the wave travels. When the particles oscillate parallel to or along the direction of the wave, the wave is a longitudinal wave.

25.6 Longitudinal Waves Both transverse and longitudinal waves can be demonstrated with a loosely coiled spring. When the end of a coiled spring is shaken up and down, a transverse wave is produced. When it is shaken in and out, a longitudinal wave is produced.

Medium When a wave travels through a medium, it does not permanently displace it. For example, when the waves in the ocean pass, the water returns to its original position.