Overview of Waves, Part 1 General wave properties through standing waves

Mechanical Waves G Require a medium (material) to carry the wave G Wave speed is determined by the medium G How quickly can material oscillate (what is the inertia/mass of the particles)? G What is the nature of the bond between particles (loose or springy) G Require a medium (material) to carry the wave G Wave speed is determined by the medium G How quickly can material oscillate (what is the inertia/mass of the particles)? G What is the nature of the bond between particles (loose or springy)

Types of mechanical waves G Transverse G Particles of medium vibrate back-and forth at a right angle to the direction of the wave motion G LINK LINK G Longitudinal G Particles of the medium vibrate back-and forth along the direction of the wave motion G LINK LINK G Transverse G Particles of medium vibrate back-and forth at a right angle to the direction of the wave motion G LINK LINK G Longitudinal G Particles of the medium vibrate back-and forth along the direction of the wave motion G LINK LINK

Wave speed in a string or wire G Recall that the medium determines the wave speed G The greater the tension F T in the wire, the faster the speed G The greater the linear density (  ) of the string, the slower the speed G Recall that the medium determines the wave speed G The greater the tension F T in the wire, the faster the speed G The greater the linear density (  ) of the string, the slower the speed

Wave speed equation G The wave speed is related to the frequency (f) of the source and the wavelength ( ) G Remember that the speed is NOT dependent on these variables, even though the equation is written this way G The wave speed is related to the frequency (f) of the source and the wavelength ( ) G Remember that the speed is NOT dependent on these variables, even though the equation is written this way

Effect of changing f G Because the wave speed is fixed by the medium, changing the frequency of the source causes a change in the wavelength G Higher f means shorter G Lower f means longer G Because the wave speed is fixed by the medium, changing the frequency of the source causes a change in the wavelength G Higher f means shorter G Lower f means longer

Electromagnetic waves (light) G The classical view of a light wave is that it is an oscillating E-field inducing an oscillating B-field and vice-versa G The sources of all light waves are vibrating charges G The classical view of a light wave is that it is an oscillating E-field inducing an oscillating B-field and vice-versa G The sources of all light waves are vibrating charges

Sound Waves G Sound waves are longitudinal pressure waves that depend on a medium to carry them G Even though they are longitudinal, they are often represented graphically by a transverse pattern representing the high and low pressure regions G Sound waves are longitudinal pressure waves that depend on a medium to carry them G Even though they are longitudinal, they are often represented graphically by a transverse pattern representing the high and low pressure regions

Doppler Effect for sound G Because the speed of the wave is fixed by the medium, a moving source or listener could perceive a shift in the frequency and wavelength

Doppler Effect for light G Light does not use a medium to propagate. However, motion of source or observer will result in a frequency and wavelength shift

Wave Interference: Linear Superposition When wave pulses overlap, they add algebraically (that is, + crest added to a - trough cancels). The wave motion is unaffected by the interaction.

Reflection of waves G When a wave is reflected from a “more resistive” material, the reflected pulse is inverted G When wave reflected from a “less resistive” material, the reflected pulse is upright G When a wave is reflected from a “more resistive” material, the reflected pulse is inverted G When wave reflected from a “less resistive” material, the reflected pulse is upright

“Standing” or “stationary” waves G When a continuous wave is reflected back upon itself, a pattern of interference develops G If the frequency and therefore wavelength match the natural vibrational frequency of the string/tube/box/atom, then a standing wave results G When a continuous wave is reflected back upon itself, a pattern of interference develops G If the frequency and therefore wavelength match the natural vibrational frequency of the string/tube/box/atom, then a standing wave results

Standing waves in a string - LINK LINK Standing waves in a string - LINK LINK

Standing sound waves