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Waves

Waves. Do the wave!!. In class on board- w/demos Wave vs particle Mechancal vs non- mechancal Longitudinal vs Transverse Spreading of waves. Intro to Waves. A disturbance which travels through a medium from one point in space to the others.

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Waves

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  1. Waves Do the wave!!

  2. In class on board- w/demos • Wave vs particle • Mechancalvs non-mechancal • Longitudinal vs Transverse • Spreading of waves Intro to Waves

  3. A disturbance which travels through a medium from one point in space to the others. I. Nature of a WaveA. Definition of wave

  4. Energy is transferred from one place to another in a wave motion. • Motion of the medium (particles of the medium) is usually periodically vibratory. • Only the shape or form of wave travels, not the medium. Properties of Waves

  5. Wave Motion A wave travels along its 
medium, but the 
individual particles just 
move up and down.

  6. Wave Motion All types of traveling waves transport energy. Study of a single wave pulse 
shows that it is begun with a 
vibration and transmitted 
through internal forces in the 
medium. Continuous waves start with 
vibrations too..

  7. Wave Motion Wave characteristics : use string and glue to create a wave- include the following label and define each characteristic. Amplitude, A Wavelength, λ Crest Trough Rest line Define the following:

  8. Amplitude • Wavelength () • Frequency (f) • Period (T) • Wave velocity (v) A wave is usually described by the following terms : Anatomy of a Wave Each term will be explained….

  9. The amplitude is the maximum displacement of the medium from its equilibrium position(rest line). The amplitude of a wave refers to the distance from the equilibrium point (or ½ the distance from highest to lowest point of vibration) • The wavelength () is the minimum distance between two points which are in phase. • Thefrequency (ƒ) is the number of complete oscillations (waves)made in one second. The frequency of a wave refers to how many “waves” pass by a point in a given amount of time (usually a second)Unit : Hz • The period (T) The period of a wave is the time for a to make one complete cycle. Period, being a time, is measured in units of time such as seconds, hours, days or years. Itis the time taken for one complete oscillation(wave). It is related to frequency by T = 1/ƒUnit : s

  10. Use construction paper- string -glue • create a transverse wave • Label parts • Crest‘- highest part off rest of transverse wave • Trough-lowest part off rest of transverse wave • Amplitude-maximum displacement off rest • Wavelength-distance between two points –crest to crest • Frequency- to how many “waves” pass by a point in a given amount of time (usually a second)the entire sheet is one second • Period-time for a wave to make one complete cycle. Transverse Paper Activity

  11. Longitudinal wave

  12. Graphing harmonic motion- using paper and string • When oscillations are small, the motion is called simple harmonic motion (shm) and can be described by a simple sine curve. • See animation

  13. Flip side of transverse wave model • create a longitudinal wave – draw slinky-like model • Label parts • Compression-Crest- particles – highest density • Rarefaction -Trough-particles stretched • Amplitude-maximum displacement off rest-compression to rest • Wavelength-distance between two points –compression to compression • Frequency- to how many “waves” pass by a point in a given amount of time (usually a second)the entire sheet is one second • Period-time for a wave to make one complete cycle. Longitudinal paper activity

  14. 1. Classification based on direction of vibration • according to the direction of vibration, waves are classified into : • (a) Transverse wave; • (b) Longitudinal waves.

  15. Types of Waves: Transverse and Longitudinal The motion of particles in a wave can either be 
perpendicular to the wave direction (transverse) 
or parallel to it (longitudinal).

  16. a. Transverse Waves • The waveform appears in the shape of sine curve. • A wave in which the motions of the matter particles are perpendicular to the direction of propagation of the wave itself. Examples Water waves, pulse in a stretched string,transverse wave demonstrator.

  17. Types of Waves: Longitudinal Sound waves are longitudinal waves:

  18. Longitudinal Waves • A wave in which the motions of the matter particles are in the same direction as the wave propagation. Sound, or a spring oscillating up and down Examples

  19. Mechanical Waves Based on medium • A material medium is necessary for the transmission for mechanical waves. Mechanical waves cannot travel through vacuum. • Due to forces on particles in the “medium” that are next to each other, the disturbance is transmitted from one layer to the next through the medium.

  20. Sound waves require a medium • Mechanical waves – require a medium to carry the energy • ie: gas liquid solid. • air, water, metal plumbing carries sound

  21. Non Mechanical Waves (Electromagnetic Waves) • Material medium is not essential for propagation. e/m waves travel through vacuum. • Disturbance of electric and magnetic fields travelling through space. • All electromagnetic waves are transverse waves. examples X-rays, radio waves, micro-waves,etc.

  22. Categories of WavesWavesare classified into different types according to their natures :

  23. A wave is an oscillation that travels. • A ball floating on water can oscillate up and down in harmonic motion. • The surface of the water oscillates in response and the oscillation spreads outward from where it started. Harmonic Motion

  24. Vibrational Motion • Vibration: in a general sense, anything that switches back and forth, to and fro, side to side, in and out, off and on, loud and soft, or up and down is vibrating. A vibration is a wiggle in time. • Wave: a wiggle in both space and time is a wave. A wave extends from one place to another. • Vibrations and waves: the source of all waves is something that is vibrating. Waves are propagations of vibrations throughout space. • Harmonic motion occurs when a vibration repeats and is converted (no energy input is needed to continue the motion) Vibrations

  25. Cycle: A cycle is a unit of motion that repeats. Properties of Periodic Motion

  26. Cpo-t and f

  27. The Wave Equation The wave velocity is the displacement traveled by the wave in one second …….... The wave velocity (v) is related to frequency and wavelength by -- The Wave Equation v = ƒ

  28. Using the Wave EquationExample : A travelling wave of wavelength 0.6m moves at a speed of 3.0 m/s. What is the period of this wave ? • = 0.6 m, • v = 3.0 m/s • f = ? By using the wave equation, v = ƒ ƒ = v/ f = (3.0 m/s)/(0.6 m)ƒ = 5.0 Hz The unit of ‘m’ cancel out—and you are left with 5.0/s which is 5.0 Hz Then the period of this wave is ??? Period T = 1/ƒ T = 1/5.0 or 0.2 s

  29. The speed of a wave equals the frequency times the wavelength. Frequency (cycles/sec) Relationship between speed, frequency, and wavelength v = f l Speed (m/sec) Wavelength (m)

  30. Calculate the wave equation using graph paper model activity • Sine curve- draw 1,2,4,5,10, 20 waves – each wave has an amplitude of 2 blocks to crest and 2 blocks to trough. CALCULATE: • Frequency-period • wavelength • Wave speed WAVE EQUATION ACTIVITY

  31. 1 What is the wave speed if the period of a wave is 
4 seconds and the wavelength is 1.8 m? 7.2 m/s B Answer

  32. 2 A fisherman noticed that a float makes 30 
oscillations in 15 seconds. The distance between 
to consecutive crests is 2 m. What is the wave 
speed? 4 m/s B Answer

  33. 3 What is the wavelength of a wave trveling with a 
speed of 6 m/s and a period of 3s? 18 m/s B Answer

  34. A. Reflection- The bouncing back of a wave when it meets a surface or boundary i. Echo- is a reflection of sound waves B. Diffraction – bending of a wave around an object I. Sound waves around a door AM waves are longer and travel around a building FM waves are shorter and can’t move around E. Refraction – bending of a wave as it passes from one medium to another i. waves travel at different speeds when passing through different mediums Demo pencil in a beaker – light travels faster in air than water

  35. Constructive interference happens when waves add up to make a larger amplitude. • Suppose you make two wave pulses on a stretched string. • One comes from the left and the other comes from the right. • When the waves meet, they combine to make a single large pulse.

  36. What happens when one pulse is on top of the string and the other is on the bottom? • When the pulses meet in the middle, they cancel each other out. • During destructive interference, waves add up to make a wave with smaller or zero amplitude.

  37. SLINKY LAB

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