Waves Waves n Waves transmit energy and information
- Slides: 68
Waves
Waves n Waves transmit energy and information. n Sound and Light are both waves.
There are two ways to transmit information/energy in our universe: Particle Motion and Wave Motion
1. VIBRATION OF A PENDULUM n Demo -Ball pendulum n What does the period (T) depend upon? Length of the pendulum (l). n Acceleration due to gravity (g). n Period does not depend upon the bob mass. n
When oscillations are small, the motion is called simple harmonic motion (shm) and can be described by a simple sine curve.
Sine Curve Wavelength Amplitude A
2. WAVE DESCRIPTION Picture of a Transverse Wave Crest Wavelength A A - Amplitude Trough
Wavelength ( ) n Distance between adjacent crests in a transverse wave n Distance a wave travels during one vibration n Units - meters or feet
Period (T) n Time required to make one vibration. n Time required to generate one wave. n Time required for the wave to travel one wavelength.
Frequency (f) The number of vibrations per unit of time made by the vibrating source. Units cycles per second 1/s Hertz (Hz)
Examples of Frequency n What is the frequency of the second hand of a clock? Frequency = 1 cycle/60 sec Period = 60 sec n What is the frequency of US Presidential elections? Frequency = 1 election/4 yrs Period = 4 yrs
Frequency Period
3. WAVE MOTION n Energy is transported by particles or waves. n A wave is a disturbance transmitted through a medium. n Exception: light does not require a medium.
Demo - Waves on a rope A disturbance moves through the medium. Elements of the medium vibrate. Examples: ripples on water wheat waves
4. WAVE SPEED The average speed is defined as
For a wave, if the distance traveled is a wavelength ( ), then the time to travel this distance is the period (T). Thus or
is true for all waves. Note: v is dictated by the medium. f is dictated by the source.
5. TRANSVERSE WAVES Particles vibrate perpendicular to the motion of the waves Slinky Transverse Waves string musical instruments ripples on water Examples: electromagnetic waves e. g. Light waves. Seismic “S”-waves.
Picture of a Transverse Wave Crest Wavelength A A - Amplitude Trough
6. LONGITUDINAL WAVES Particles vibrate Parallel to the motion of the waves - Slinky Longitudinal Waves e. g. Sound. Seismic P-waves.
Parameters Rarefactions are regions of low density. Compressions (condensations) are regions of high density. is the distance between…. . . …………. successive rarefactions or …………. successive compressions.
Demo - Slinky
7. Super position INTERFERENCE Superposition of Waves Overhead - Interference
Superposition A number of different waves can add, constructively or destructively. n The superposition of two or more waves results in interference.
Interference The superposition of two or more waves results in interference. n
Interference Pattern The pattern formed by superposition of different sets of waves that produce mutual n reinforcement in some places and cancellation in others.
Destructive Interference: Exactly out of Phase Cancellation + Zero displacement
Destructive interference occurs when waves are out of phase, that is when crests are superimposed with troughs.
Constructive Interference: Reinforcement + Maximum In phase displacement
Constructive Interference occurs when waves are in phase, that is when crests are superimposed and troughs are superimposed.
Constructive and Destructive Interference www. phy. ntnu. edu. tw/j ava/wave. Interference/w ave. Interference. html
Interference is a characteristic of all waves.
Standing Waves n When two sets of waves of equal amplitude and wavelength pass through each other in opposite directions, it is possible to create an interference pattern that looks like a wave that is “standing still. ” Demo - Rope and strobe n Demo - Mechanical overhead model n
Standing Wave V Incident Wave V Reflected Wave V Standing Wave V
Standing Waves
n There is maximum vibration at an antinode. n is twice the distance between successive nodes or successive antinodes. n There is no vibration at a node.
Notes on Standing Waves n There is no vibration at a node. n There is maximum vibration at an antinode. n is twice the distance between successive nodes or successive antinodes.
n Demo- Soda straw wave machine n Demo - tuning fork n Another example: musical instruments n Demo- Drumhead Vibrations
8. DOPPLER EFFECT n Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves n Doppler with Sound n www. physics. sfasu. e du/markworth/doppler. htm
Doppler Effect The shift in received frequency due to motion of a vibrating source toward or away from a n receiver.
Doppler Effect Notes Motion of Source and Observer Moving together Moving Apart Sound Light Higher Pitch Lower Pitch “Blue Shift” “Red Shift”
Doppler Shift Gives Radial Velocity True Velocity Radial Velocity Tangential Velocity Radar
Red Shift Lab Absorption Spectrum of Element X Red Shifted Star Absorption Spectrum of Element X Star is moving away from us.
Bow Wave The V-shaped wave made by an object moving across a liquid surface at a speed greater than n the wave speed. (Since the source is moving faster than the wave speed, the wavefronts pile up. )
9. BOW WAVES n Waves in front of moving object pile up. n Demo - Barrier slide n Demo - “Bow” wave slide
Shock Wave The cone-shaped wave made by an object moving at supersonic speed through a fluid. n (Here, the source is moving faster than the wave speed, which is the speed of sound!!) (Super-sonic speed)
10. SHOCK WAVES n Demo - Cone of Waves n There are two booms, one from the front of the flying object and one from the back.
Shock Wave
Sonic Boom The loud sound resulting from the incidence of a shock wave. (This n is the result of the pile up of many wave fronts which produces a sonic boom)
Sonic Boom Piled up wave n fronts produce a shock wave Plane
Shock Wave
Sonic booms from a plane are produced (a) because the plane breaks through the sound barrier (b) when the plane reaches the speed of sound (c) by the plane traveling faster than the speed of sound (d) by the plane traveling slower than the speed of sound
Twice the speed of sound Mach 2 Wave front n 1 unit Plane 2 units
n Demo - Crack whip n Wav File - Sonic Boom n The boom is not produced just when the flying object “breaks” through the sound barrier.
n. Subsonic - slower than the speed of sound n Supersonic - faster than the speed of sound speed of object n Mach Number = speed of sound
Review Questions
Doubling the mass of a simple pendulum undergoing small oscillations does what to the period of the pendulum? (a) cuts it in half (b) increases it by the square of 2 (c) nothing (d) doubles it
What dictates the frequency of a sound wave? (a) wavelength (b) medium (c) source of the sound (d) speed (e) amplitude
What determines the speed of a wave? (a) the frequency (b) the wavelength (c) the amplitude (d) the period (e) the medium of transmission
A skipper on a boat notices wave crests passing his anchor chain every 5 seconds. If the wave crests are 15 m apart, what is the speed of the water waves in m/s? (a) 5 (d) 10 (b) 15 (e) 3 (c) 75
For a medium transmitting a longitudinal wave, the areas of the medium where the density of the medium is temporarily increased are called. . . (a) rarefactions (b) compressions (c) density holes
When you move away from a fixed source of sound, the frequency of the sound you hear. . . (a) is greater than what the source emits (b) is less than what the source emits (c) is the same as what the source emits
Sonic booms from a plane are produced. . . (a) because the plane breaks through the sound barrier. (b) when the plane reaches the speed of sound. (c) by the plane traveling faster than the speed of sound. (d) by the plane traveling slower than the speed of sound.
- Waves that transmit energy through matter or empty space
- Transmit waves
- Mechanical waves and electromagnetic waves
- Store and transmit genetic information
- Introduction to the giver
- Transmit diversity in lte
- Neuron physiology
- Ce este un dialog
- Automatic transmit power control
- Transmit light
- Hui transmit data
- Energy energy transfer and general energy analysis
- Energy energy transfer and general energy analysis
- Compare and contrast p waves and s waves using venn diagram
- Differences between mechanical and electromagnetic waves
- Examples of mechanical waves
- How are rainbows made
- Short wave vs long wave radiation
- Mechanical waves and electromagnetic waves similarities
- Mechanical waves and electromagnetic waves similarities
- Surface waves and body waves
- Aimtoknow
- Light is electromagnetic wave true or false
- What type of waves are sound waves? *
- Sound is a longitudinal wave
- Examples of mechanical and electromagnetic waves
- Seismic waves are mechanical waves
- What is sound
- Kesler science
- Waves energy transfer
- How radio waves carry information
- Wave transfer matter
- Energy density in em waves
- Rate of energy transfer by sinusoidal waves on strings
- What is a repeating disturbance
- Wave transfers
- Electromagnetic waves obey principle of .. *
- Energy carried by electromagnetic waves
- Do light waves transfer energy
- Solar radiant energy is composed of short waves
- Section 2 describing energy
- Primary energy and secondary energy
- Hypdro
- Helmholtz free energy
- Renewable energy and energy efficiency partnership
- Kinetic energy examples
- Conservation of mechanical energy
- Potential energy
- Kinetic energy and potential energy formula
- Energy forms and energy conversions
- Imperfect information vs incomplete information
- Ceii ferc
- Energy information administration
- Spring potential energy
- Gibbs free energy non standard conditions
- Standard free energy change
- Efficiency formula
- Thermal energy vs heat energy
- A hairdryer converts ____ energy into ____ energy.
- Practical electricity formulas
- How to convert mechanical energy to electrical energy
- Thermal energy section 3 using thermal energy
- How to find delta g
- As nutritional energy passes through the food chain it is
- Usable chemical energy in food begins as __________ energy.
- Chapter 7 energy conservation of energy
- Wind energy is an indirect form of solar energy
- ________ converts light energy into chemical energy. *
- Formula of potential and kinetic energy