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4.1 – Properties of Waves

Explore the essential features of waves, including amplitude, wavelength, and frequency. Learn about different wave types like transverse and compression waves. Understand how waves interact with various media and their real-world applications.

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4.1 – Properties of Waves

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  1. 4.1 – Properties of Waves

  2. 4.1 – Features of a Wave • To study optics, some starting vocabulary is needed • Wave • A disturbance or movement that transfers energy through matter or space, without causing any permanent displacement • Energy • The capacity to apply a force over a distance, or the ability to perform work • Force • A push or a pull on an object

  3. 4.1 – Features of a Wave • The dotted line represents the equilibrium or rest position • Remember from section 1.3 • An equilibrium is a balance in a system between opposing forces or quantities, like concentration of height

  4. 4.1 – Features of a Wave • Notice the new terms: • Crest • The highest point in a wave • Trough • The lowest point in a wave

  5. 4.1 – Features of a Wave • One of the most important properties of waves is its amplitude • Amplitude • The height of a crest or the depth of a trough, measured from the equilibrium position

  6. 4.1 – Features of a Wave • Another important property of waves is its wavelength • Wavelength • The distance from one crest to the next, or one trough to the next • Also the distance to complete one crest and one trough

  7. 4.1 – Features of a Wave • Another important property of waves is its frequency • Frequency • The number of repetitive motions that occur in a given time

  8. 4.1 – Features of a Wave • Amplitude • The units of amplitude depend on what kind of wave it is • Sound  decibels (dB) • Light  volts per meter (V/m) • Wavelength • Measured in metres (millimetres, micrometres, etc.) • Frequency • Measured in: • Hertz (Hz) • The number of cycles per second

  9. 4.1 – Features of a Wave • Frequency and wavelength have an inverse relationship • Inverse relationship (inversely proportional) • When one value increases as the other decreases • As the wavelength increases, the frequency decreases

  10. 4.1 – Features of a Wave • Frequency, wavelength and amplitude relate to properties we recognize • Frequency and wavelength • The colour of visible light • Red  400 – 484 THz • Blue  668 – 789 THz • The pitch of sound • C4 (middle C)  261.6 Hz • C5  523.3 Hz

  11. 4.1 – Features of a Wave • Frequency, wavelength and amplitude relate to properties we recognize • Amplitude • A higher amplitude means the wave carries more energy • How bright a light is • The higher the amplitude, the brighter the light • The volume of sound • Softest sound you can hear  0 dB • Breathing  10 dB • Typical library  40 dB • Typical conversation  50 – 60 dB • Busy street  90 dB • Typical concert  120 – 150 dB • Eardrum rupture  >175 dB

  12. 4.1 – Two Types of Waves • Most types of waves require something to travel through • Medium • The matter (a solid, liquid, gas or combination of these) that a wave travels through • Sound waves  medium is air • Ocean waves  medium is water • Not all waves require a medium • Light travels the fastest through a vacuum • Different types of waves interact differently with a medium (section 4.2) • Sound speeds up as the medium gets denser • Light slows down as the medium gets denser

  13. 4.1 – Two Types of Waves • Cherenkov radiation • When light travels through water, it does so at 75% of its maximum speed • Electrons in the water can therefore travel faster than the slowed-down light, producing this blue glow

  14. 4.1 – Two Types of Waves • Type 1 • Transverse wave • A wave in which the matter of the medium moves up and down, at 90 degrees to the direction of wave travel • Examples • Flicking a rope up and down • Light waves • “The Wave” • Think about it – the wave moves left or right, but you move up and down

  15. 4.1 – Two Types of Waves • Type 2 • Compression wave • A wave in which the medium moves back and forth along the same direction that the wave travels • Example • Sound • Air compresses and expands, pushing sound energy through the air

  16. 4.1 – Two Types of Waves • Earthquakes feature both types of waves • P waves (primary waves) • Compression waves • Can travel through any medium • Travel the fastest, so they arrive first • S waves (secondary waves) • Transverse waves • Can only travel through solids • Travel slower than P waves, so they arrive second

  17. Pg 142 – Active Noise Cancellation • Multiple waves can overlap • When they do, their amplitudes add together • Amplitudes above the equilibrium are positive • Amplitudes below the equilibrium are negative • We can use this • Noise cancelling headphones have a microphone and a signal processor • The microphone measures the background noise • The signal processor analyzes the signal and identifies the positive sound wave • The sound that is heard, but will be blocked

  18. Pg 142 – Active Noise Cancellation • The headphone speakers then produce another sound wave that has the complete opposite shape of the positive wave • This is called the negative wave • The positive and the negative waves cancel each other out

  19. 4.1 – Properties of Waves • Homework break #1 • Reading Check • Pg 138, #1-5

  20. 4.1 – Properties of Waves

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