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Mav Mark 9/15/11

Mav Mark 9/15/11. Name three different types of waves. Characteristics of Waves. Part 1. Waves and Energy. A wave is a type of mov’t that carries energy from place to place. Energy is what you need to do work.

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Mav Mark 9/15/11

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  1. Mav Mark9/15/11 • Name three different types of waves.

  2. Characteristics of Waves • Part 1

  3. Waves and Energy • A wave is a type of mov’t that carries energy from place to place. Energy is what you need to do work. • If you shake one end of a rope up and down, a wave travels through the rope. The wave in the rope carries energy from your hand.

  4. Waves and Energy • A mechanical wave is a wave that must have material to travel through. The material a mechanical wave travels through is called a medium. • A wave in a rope is a mechanical wave. The rope is the medium.

  5. Waves and Energy • Conversely, Electromagnetic waves do not require a medium to transfer energy. • Visible light and radio waves are examples of electromagnetic waves.

  6. Waves and Energy • A mechanical wave starts with a vibration. A vibration is a repeated up-and-down or back-and-forth movement. • The vibration that starts a rope wave is the up-and-down mov’t of your hand.

  7. Types of Mechanical Waves • Transverse waves move the medium up and down. A wave in a rope is a transverse wave. • Longitudinal waves move the medium back and forth. A wave in a spring toy (Slinky) is a longitudinal wave.

  8. Parts of a Wave • A transverse wave is composed of two parts. • A crest is the highest point of the wave. • A trough is the lowest point of a wave.

  9. Parts of a Wave • A longitudinal wave is composed of two parts. • Compressions are the parts of the wave that are closest together. • Rarefactions are the parts of the wave that are spread out.

  10. Properties of Waves • Amplitude is how far the medium moves when a wave passes through it. • For a transverse wave, amplitude is how far the medium moves up or down. For a longitudinal wave, amplitude is how far the medium moves back or forth. • Amplitude shows how much energy the wave has. The more energy the wave has, the bigger the amplitude of the wave.

  11. Properties of Waves • Wavelength is how far a wave travels before it starts to repeat. To find the wavelength of a transverse wave, you can measure the distance between the crest of one wave to the crest of the next wave. Or the distance between to adjacent troughs. • Wavelength is usually represented by the Greek letter lambda (λ).

  12. Properties of Waves • Frequency is the number of waves that go by a point in a certain amount of time. • Frequency is measured in units called hertz (Hz). If one wave passes a point each second, the frequency is 1Hz. If two waves pass a point each second, the frequency is 2Hz. • Remember electricity, where 1 coulomb per second = 1 amp. This is known as current. • In waves, 1 wave per second = 1Hz. This is known as frequency. • This is named after Heinrich Hertz, who is the German scientist who discovered radio waves.

  13. Properties of Waves • Speed is how far a wave travels in a given amount of time. • For example, if a wave travels 5cm in 1 second, its speed is 5cm per second. • Therefore, • Speed = Wavelength x Frequency • or • speed (m/s) = λ (m) × f (Hz)

  14. Wave Speed s = Speed measured in meters per second (m/s) f = Frequency measured in Herts (Hz) s λ f λ = wavelength measured in meters

  15. Wave Speed • A wave has a length of 4cm, and a frequency of 1 wave per second. What is the wave’s speed?

  16. Wave Speed • A wave is found to be 3m long and travels at 4 waves per second. What is its speed?

  17. Wave Speed • A wave is traveling at 10 m/s and has a length of 14 mm. What is the wave’s frequency?

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