University:
Winston-Salem Forsyth County Schools
Course:
AP Physics I
Academic year:

2015
Views:

450

Pages:

98
Author:

litofanievqgf

Waves Chapter 10 Section 1 The Nature of Waves Waves    The Nature of Waves slides 1-20 Wave Properties slides 21- 46 The Behavior of Waves slides 46 -97 Waves  A wave is a repeating disturbance or movement that transfers energy through it. Waves   A wave is a repeating disturbance or movement that transfers energy through it. Examples: Microwaves  Radio waves  Sound waves  Ocean waves  Waves and Energy  A pebble falling into a pool causes a disturbance which transfers energy to the water molecules nearby which in turn pass the energy along to molecules that are next to them. A wave is formed that carries the energy along the surface of the water. Do waves carry matter?   A boat on a lake may move up and down or even back and forth a little with a wave but is not carried to a different position. The wave ONLY carries energy without moving matter. How can you make a wave?  A wave will travel as long as there is both energy & a medium to carry it. How can you make a wave?    A wave will travel as long as there is both energy & a medium to carry it. Anything that moves up & down or back and forth is a vibrating movement. Vibrations cause all waves. Mechanical Waves  A medium is the matter through which a wave travels. It can be solid, liquid, or gas or a combination. Mechanical Waves   A medium is the matter through which a wave travels. It can be solid, liquid, or gas or a combination. Light and radio waves do not need a medium & can travel through space. Mechanical Waves    A medium is the matter through which a wave travels. It can be solid, liquid, or gas or a combination. Light and radio waves do not need a medium & can travel through space. Waves that can only travel through a medium are called mechanical waves. Transverse  Compressional  Mechanical Waves  Waves that can only travel through a medium are called mechanical waves. Transverse- the matter in the medium moves at a right angle to the direction the wave travels; ex. Ocean wave  Compressional (longitudinal)- matter moves back and forth in the same direction that the wave travels ex. spring  Mechanical Waves Transverse Wave Compressional Waves How do sound waves move?  Sounds waves are compressional waves which travel through air, water, and wood. When the sound wave reaches your ear, it causes your eardrum to vibrate, sending signals to your brain which you understand as sound. How do water waves move?  Water waves are a combination of transverse & compressional waves. The water moves up & down & back & forth ending up where it began. How do ocean waves move?  Wind blowing across the ocean surface causes most ocean waves to form. How do ocean waves move?   Wind blowing across the ocean surface causes most ocean waves to form. Size of the wave depends on: Speed of the wind  Length of time the wind blows  How far it travels over the water  What are seismic waves?  Seismic waves are a combination of transverse & compressional waves that carry energy outward and cause an earthquake. Mechanical Waves Transverse Waves How they move example Compressional waves How they move example Mechanical Waves Transverse Waves Compressional waves How they move How they move the matter in the medium moves at a right angle to the direction the wave travels matter moves back and forth in the same direction that the wave travels example Ocean waves example Spring or slinky, sounds Wave Properties Chapter 10 Section 2 Parts of a Wave    Crest Trough Rarefaction Parts of a Wave    Crest – high point of a transverse wave Trough – low point of a transverse wave Rarefaction – area where the medium is more spread out Compressional Wave  Rarefaction – area where the medium is more spread out Parts of a Wave  Wavelength- distance b/w one point on a wave and the nearest point just like it. Human Hearing  Only hear sounds that have wavelengths with measures between a few cm and about 15 m. Frequency and Period  Frequency- number of wavelengths that pass by a point each second, expressed in Hz (hertz) ex. Choosing radio station. Frequency and Period   Frequency- number of wavelengths that pass by a point each second, expressed in Hz (hertz) ex. Choosing radio station. Period- amount of time it takes one wavelength to pass a point, measured in seconds. How are frequency & wavelength related?  As the frequency of waves increases, their wavelength decreases Wave Speed  Light waves travel through gases much faster than sound waves. Wave Speed   Light waves travel through gases much faster than sound waves. The speed of a wave depends on the medium it is traveling through. Wave Speed    Light waves travel through gases much faster than sound waves. The speed of a wave depends on the medium it is traveling through. Sound waves (compression) usually travel faster than light waves through liquids and solids. Wave Speed     Light waves travel through gases much faster than sound waves. The speed of a wave depends on the medium it is traveling through. Sound waves (compression) usually travel faster than light waves through liquids and solids. Sound waves usually travel faster in a material if the temperature of the material is increased. How do you calculate wave speed?  Calculate speed by multiplying its frequency times its wavelength. The Greek letter lambda (λ) represents wavelength, f is frequency, and v represents the speed of the wave. How do you calculate wave speed?   Calculate speed by multiplying its frequency times its wavelength. The Greek letter lambda (λ) represents wavelength, f is frequency, and v represents the speed of the wave. Speed (m/s) = frequency (Hz) X wavelength ( in m) or v=f λ How do you calculate wave speed?    Calculate speed by multiplying its frequency times its wavelength. The Greek letter lambda (λ) represents wavelength, f is frequency, and v represents the speed of the wave. Speed (m/s) = frequency (Hz) X wavelength ( in m) or v=f λ What is the speed of a sound wave that has a frequency of 150 Hz and a wavelength of 0.00002 mm? Show your work. How do you calculate wave speed?   What is the speed of a sound wave that has a frequency of 150 Hz and a wavelength of 0.00002 mm? Show your work. F = 150 Hz λ = 0.00002 mm How do you calculate wave speed?    What is the speed of a sound wave that has a frequency of 150 Hz and a wavelength of 0.00002 mm? Show your work. F = 150 Hz V=f λ= λ = 0.00002 mm How do you calculate wave speed?    What is the speed of a sound wave that has a frequency of 150 Hz and a wavelength of 0.00002 mm? Show your work. F = 150 Hz λ = 0.00002 mm V = f λ = 150 Hz X 0.00002 mm How do you calculate wave speed?     What is the speed of a sound wave that has a frequency of 150 Hz and a wavelength of 0.00002 mm? Show your work. F = 150 Hz λ = 0.00002 mm V = f λ = 150 Hz X 0.00002 mm V = .003 mm/s Amplitude and Energy  Amplitude – measure of the energy that a wave carries. The greater the amplitude, the more energy the wave carries. Amplitude and Energy   Amplitude – measure of the energy that a wave carries. The greater the amplitude, the more energy the wave carries. Compressional waves amplitude depends on how tightly the medium is pushed together at the compressions. Amplitude and Energy    Amplitude – measure of the energy that a wave carries. The greater the amplitude, the more energy the wave carries. Compressional waves amplitude depends on how tightly the medium is pushed together at the compressions. Transverse waves amplitude = distance from the crest or trough of the wave to the rest position Properties of waves Wavelength Energy Frequency Properties of waves Period Amplitude Wave speed The Behavior of Waves Chapter 10 Section 3 Reflection  Wave reflection happens when a wave strikes an object or surface and bounces off of it. Reflection   Wave reflection happens when a wave strikes an object or surface and bounces off of it. All types of waves, including sound, water, and light waves, can be reflected. How do light waves reflect?  Light waves strike canal houses in Amsterdam; then the reflected waves strike water in the canal and bounce off creating this image captured by the camera. Law of Reflection  The light beam striking the mirror is called the incident beam. Law of Reflection   The light beam striking the mirror is called the incident beam. The line that is at a right angle to the mirror is called the normal. Normal Law of Reflection    The light beam striking the mirror is called the incident beam. The line that is at a right angle to the mirror is called the normal. The light beam that bounces off the mirror is called the reflected beam. Normal Law of Reflection  The angle made by the incidence beam and the normal is the angle of incidence. Angle of incidence Normal Law of Reflection   The angle made by the incidence beam and the normal is the angle of incidence. The angle made by the reflected beam and the normal is the angle of reflection. Angle of incidence Normal Angle of reflection Law of Reflection  The law of reflection says that the angle of incidence is equal to the angle of reflection. Angle of incidence Normal Angle of reflection What are echoes?  Echoes are reflected sound waves. What are echoes?   Echoes are reflected sound waves. If a sound is not absorbed or transmitted when it strikes a surface, it will be reflected. What are echoes?    Echoes are reflected sound waves. If a sound is not absorbed or transmitted when it strikes a surface, it will be reflected. The law for reflection is the same as that for light, i.e. the angle of incidence of a sound wave equals the angle of reflection. Refraction  Can you recall seeing an object in water that appears to be broken? Refraction   Can you recall seeing an object in water that appears to be broken? A waves speed depends on the medium it is passing through; changing mediums may change speeds of the wave. Refraction   Can you recall seeing an object in water that appears to be broken? A waves speed depends on the medium it is passing through; changing mediums may change speeds of the wave. Refraction is the bending of a wave caused by a change in its speed as it moves from one medium to another. Refraction  Two things happen to the light waves as they move from the air to the water in the glass.   Change speed Change direction Refraction  As the light wave slows down, it bends toward the normal. Refraction/Reflection   As the light wave slows down, it bends toward the normal. As the light wave speeds up, it bends away from the normal. Diffraction  Diffraction takes place when an object causes a wave to change direction and bend around it. Diffraction   Diffraction takes place when an object causes a wave to change direction and bend around it. Example: hearing sound coming from another room. Diffraction    Diffraction takes place when an object causes a wave to change direction and bend around it. Example: hearing sound coming from another room. Light waves do not refract as much as sound waves though they do bend around edges. When do water waves diffract?  Ocean waves diffract when they strike an island. They change direction and bend around the island. When do water waves diffract?   Ocean waves diffract when they strike an island. They change direction and bend around the island. Waves diffract when they pass through a narrow opening spreading out afterwards, bending around the corners of the opening. How much will a wave bend?  Compare the size of the object to the wavelength: How much will a wave bend?  Compare the size of the object to the wavelength: Smaller object, waves bend around it making narrow shadow  Object larger than the wavelength, creates wider shadow because the light waves can’t bend as easily.  How much will a wave bend?  Compare the size of the object to the wavelength: Smaller object, waves bend around it making narrow shadow  Object larger than the wavelength, creates wider shadow because the light waves can’t bend as easily.  This is the shadow of a razor blade. How do sound waves bend around corners?  Wavelengths of sound are about the same size as the door opening so they diffract and spread into the hallway. How do sound waves bend around corners?   Wavelengths of sound are about the same size as the door opening so they diffract and spread into the hallway. This is different than from light waves which have a shorter wavelength than sound waves, thus light waves are not diffracted around the door as much as sound waves. How do radio waves differ?  AM (amplitude modulated) radio waves have longer wavelengths than FM (frequency modulated) radio waves. How do radio waves differ?   AM (amplitude modulated) radio waves have longer wavelengths than FM (frequency modulated) radio waves. This means that AM waves can diffract around objects like buildings and mountains much more than FM radio waves. Interference  Interference is the point where two waves meet each other and overlap to form a new wave. Interference   Interference is the point where two waves meet each other and overlap to form a new wave. The new wave lasts only as long as the two waves continue to overlap. Interference    Interference is the point where two waves meet each other and overlap to form a new wave. The new wave lasts only as long as the two waves continue to overlap. There are two kinds of interference: Constructive  Destructive  Interference    Interference is the point where two waves meet each other and overlap to form a new wave. The new wave lasts only as long as the two waves continue to overlap. There are two kinds of interference: Constructive- waves meet and add together  Destructive- waves overlap and subtract from each other.  Constructive Interference Constructive Interference  The amplitudes add together to make a larger wave with a higher crest and a lower trough. Constructive Interference   The amplitudes add together to make a larger wave with a higher crest and a lower trough. The amplitude of the new wave is the sum of the amplitudes of the other two waves. Destructive Interference Destructive Interference  The amplitudes combine together to make a smaller wave with a lower crest and a higher trough. Destructive Interference   The amplitudes combine together to make a smaller wave with a lower crest and a higher trough. The amplitudes cancel each other out in both transverse & compressional waves. Standing Waves  A standing wave is a wave pattern that forms when two equal-sized waves travel in opposite directions and continuously interfere with each other.  Nodes where two waves cancel each other What are some examples of standing waves?  Musical instruments:    Violin- bow creates standing waves in the strings Flute creates standing waves in a column of air Drums vibrate to make standing waves Resonance  All objects have their own natural frequencies of vibration. Resonance   All objects have their own natural frequencies of vibration. Frequencies depend on the size and shape of the object and what it is made of. Resonance    All objects have their own natural frequencies of vibration. Frequencies depend on the size and shape of the object and what it is made of. Resonance is when an object vibrates by absorbing energy from another object that is vibrating at its natural frequency. Resonance  Resonance can cause an object to absorb so much energy that it vibrates too much and breaks apart. Resonance   Resonance can cause an object to absorb so much energy that it vibrates too much and breaks apart. These are pictures of the Tacoma Narrows Bridge collapse on Nov. 7, 1940, that was caused by 42 mph winds creating a resonant response (28 ft waves) by the bridge which was over 1 mi long. Skill Builder Concept Map  Show the series of events that occur to produce sound. Use rarefaction, vibration & compression. Skill Builder Concept Map  Show the series of events that occur to produce sound. Use rarefaction, vibration & compression. Vibration of matter Skill Builder Concept Map  Show the series of events that occur to produce sound. Use rarefaction, vibration & compression. Vibration of matter Compression of the medium Skill Builder Concept Map  Show the series of events that occur to produce sound. Use rarefaction, vibration & compression. Vibration of matter Compression of the medium Repeats as the sound wave travels through the medium Rarefaction of the medium http://www.archive.org/details/Pa2 096Tacoma