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The Nature and Properties of Waves. Section 11.1 & 11.2. SC Standards Covered. Standard PS-7.1 Illustrate ways that the energy of waves is transferred by interaction with matter (including transverse and longitudinal/compressional waves).
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The Nature and Properties of Waves Section 11.1 & 11.2
SC Standards Covered • Standard PS-7.1 Illustrate ways that the energy of waves is transferred by interaction with matter (including transverse and longitudinal/compressional waves). • Standard PS-7.2 Compare the nature and properties of transverse and compressional mechanical waves • Standard PS-7.3 Summarize characteristics of waves (including displacement, frequency, period, amplitude, wavelength, and velocity as well as the relationships among these characteristics).\ • Standard PS-7.4 Use the formulas v = fλ and v = d/t to solve problems related to the velocity of waves.
What’s in a Wave? • Wave – a rhythmic disturbance that transfers energy through matter or space • Carries energy without transporting matter from place to place
Mechanical Waves • medium – solid, liquid, or gas that a wave travels through • Two types of mechanical waves: • Transverse • Compressional/ Longitudinal
Transverse Waves • Transverse waves – matter moves in the medium back and forth at right angles to the direction that the wave is traveling • Light waves & water waves
Compressional Waves • Compressional waves – matter in the medium moves back and forth in the same direction that the wave travels • Sound waves
Seismic Waves • Seismic waves – combination of transverse and compressional waves which carry energy along and through Earth
The Parts of a Wave • Crest – the highest points of a wave • Trough – the lowest points of a wave
Compression – place in compressional wave where the particles are pushed together • Rarefaction – place in compressional wave where the particles are spread apart
Wavelength • Wavelength – the distance between one point on a wave and the nearest point just like it
Frequency and Period • Frequency – the number of waves that pass a given point each second • Measured in Hertz = 1/sec • Period: The amount of time it takes one wavelength to pass a point
Period and frequency relationship • T = period • f = frequency Period Frequency T= 1/f f = 1/T One hertz is equal to one peak (or cycle) per second. 1/sec
Frequency and Wavelength • Frequency and wavelength are inversely related • Long wavelength = Low frequency • Short wavelength = High Frequency
Wave Speed • The speed of a wave depends on the properties of the medium it is traveling through • In general sound waves travel the fastest through solids then liquids then gases • Light waves travel the fastest in empty space and slowest through solids • Sound waves travel faster through warmer mediums
Calculating Wave Speed • Speed = wavelength x frequency • V = λ x f • V = velocity (m/s) • λ = wavelength (m) • f = frequency (Hz; 1/sec)
Example #1 • What is the speed of a wave with a wavelength of 2m and a frequency of 3 Hz? V = λ x f V = (2)(3) V = 6 m/s
Example #2 • A wave is traveling at a speed of 12 m/s and its wavelength is 3m. Calculate the wave’s frequency. V = λ x f 12 = (3)(f) 12 = f 3 4 Hz = f
Do these on your own • A tuning fork has a frequency of 280 Hertz and the wavelength of the sound produced is 1.5 meters. Calculate the velocity of the wave. • A wave is moving toward shore with a velocity of 5.0 m/s. If its frequency is 2.5 hertz, what is its wavelength?
Amplitude and Energy • Amplitude – the energy carried by a wave or how high the wave is; related to the amount of energy • For compressional waves it’s the amount of compression in the wave • Example: The higher the wave, the more energy (THINK on ocean waves)
