2 OBJECTIVES To understand the meaning of wave motion To distinguish between longitudinal and transverse wavesTo define amplitude, wavelength, period and frequency and state the relationship between themTo understand the meaning of crest and trough
3 OBJECTIVES ( CONTD.)To find amplitude and period from a displacement- time graphTo find amplitude and wavelength from a displacement- position graphTo use v = λf
4 WAVE MOTIONHow is wave motion different from the kind of motion you have studied so far?
5 WAVE MOTIONWave is a way of transferring energy from one place to another without the actual large scale motion of a material body.Light from the Sun warms up the earthA soprano singing can break a crystal glass
6 WAVE & DISTURBANCEA wave is always associated with a disturbance
7 DEFINITION OF WAVEA wave is a disturbance that transfers energy from one place to anotherThe direction of energy transfer is the direction of propagation of the wave
8 MECHANICAL WAVES Require medium for propagation Sound waves, waves in a string, water waves are mechanical waves
9 ELECTROMAGNETIC WAVES Do not require medium for propagationLight is an electromagnetic wave
10 Wave & Particle MotionThe wave, does exhibit a net displacement in space, whereas,the particles of the medium exhibit onlyoscillatory motion around their equilibrium positions.
12 Longitudinal WavesVibration direction parallel to wave propagation directionParticles in medium move closer together/farther apartExample: sound wavesGases and liquids - support only longitudinal waves
13 Sound WavesSound waves are longitudinal waves, similar to the waves on a Slinky:Here, the wave is a series of compressions and stretches.
14 Sound WavesIn a sound wave, the density and pressure of the air (or other medium carrying the sound) are the quantities that oscillate.
18 Water waves are a combination of transverse and longitudinal waves.
19 WavelengthThe length of a full wave is called the wavelength, λ , and the time needed to produce one full wave is the time period T.
20 Speed of the WaveThe wave moves forward a distance equal to a wavelength in a time equal to one time periodThe speed of the wave = distance / timev = λ / TNumber of waves produced in one second= frequency, ff = 1 / Tv = λ f..\Desktop\PhET-1.0-windows-installer.exe
21 Graphical Representation of Waves Displacement- time graphDisplacement – position graph
22 Parameters Distance : where along the wave are we looking Time: at what time are we looking at the waveDisplacement : measures the disturbance
23 More on displacementString: the height of a point on the string from the undisturbed position of the string and is measured in units of lengthSound: the change in the density of the medium relative to the equilibrium density and is measured in units of densitySound: the change in the pressure of the medium relative to the equilibrium pressure
24 Displacement All waves have a displacement The displacement is the difference of some quantity and the equilibrium value of that quantity when no wave is presentThe displacement of any waves is a function of position( distance) and time
25 Crest & TroughsAmplitude: the maximum displacement of the wave is called amplitudeCrest: Points on the wave with maximum positive displacement are called crestsTroughs: Points on the wave with maximum negative displacement are called troughs
26 Wavelength & Period from Graphs The distance between successive crests/ troughs in a displacement- distance graph is the wavelengthThe distance between successive crests/ troughs in a displacement – time graph is the time period.