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Chapter 14 Waves.   Wave   a repeating disturbance or movement that transfers energy through matter or space   A rhythmic disturbance that carries.

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Presentation on theme: "Chapter 14 Waves.   Wave   a repeating disturbance or movement that transfers energy through matter or space   A rhythmic disturbance that carries."— Presentation transcript:

1 Chapter 14 Waves

2   Wave   a repeating disturbance or movement that transfers energy through matter or space   A rhythmic disturbance that carries energy through matter or space.   Molecules pass energy on to neighboring molecules   Waves carry energy without transporting matter   All waves are produced by something that vibrates   Medium - material which a wave travels thru   May be solid, liquid, or gas   Not all waves need a medium to travel through   Example: Light waves   Wave Pulse   A single bump or disturbance that travels through a medium

3  Mechanical waves  waves that can travel only through matter  Transverse waves  matter in the medium moves back and forth at right angles to the direction that the wave travels.  Example: Water waves  Longitudinal or Compressional waves  matter in the medium moves in the same direction that the wave travels.  Example: Sound waves  Surface Waves  Combination of both transverse or compressional  examples: water waves, seismic waves

4   Ways waves differ   1. How much energy they carry   2. How fast they travel   3. How they look   Transverse waves have crests & troughs   Crest —the highest points   Troughs—the lowest points.   Compressions   Dense regions of compressional waves   Rarefactions   Less dense regions of compressional waves

5  Wavelength (λ)  the distance between one point in the wave and the nearest point just like it  Frequency (f)  how many wavelengths pass a fixed point each second  Expressed in hertz (Hz)  As frequency increases, wavelength decreases.  The frequency of a wave equals the rate of vibration of the source that creates it.

6   Wave velocity, v   describes how fast wave moves forward   velocity = wavelength * frequency   Speed of a wave = v = λ*f   f = 1/T = 1/period   Light waves travel faster than sound waves   Sound waves travel faster in liquids and solids than in gas   Light waves travel faster in gases and empty space than in liquids & solids

7  Amplitude  a measure of the energy in a wave  More energy a wave carries, the greater its amplitude.  Amplitude of compressional waves is related to how tightly the medium is pushed together at the compression  The denser the compressions, the larger the amplitude is and the more energy the wave carries  The less dense the rarefactions, the larger the amplitude and the more energy the wave carries  Amplitude of transverse waves  The distance from the crest or trough of a wave to the normal position of the medium  Ex. how high ocean wave appears above water level

8  Reflection occurs when a wave strikes an object and bounces off of it.  All types of waves can be reflected.  The angle of incidence always equals the angle of reflection  Normal  An imaginary line that is perpendicular to reflective surface

9  Incidence Wave  The wave that strikes the boundary  Angle of incidence  the angle formed by the wave striking the surface and the normal  Angle of reflection  angle formed by reflected wave and normal  Refraction  bending of a wave caused by a change in its speed as it moves from 1 medium to another

10  The greater the change in speed is, the more the wave bends.  When a wave passes into a material that slows it down, the wave is bent toward the normal.  When a wave passes into a material that speeds it up, the wave is bent away from the normal.  Diffraction  an object causes a wave to change direction and bend around it  If obstacle is smaller than wavelength, wave diffracts a lot  If obstacle is larger than wavelength, wave does not diffract much  The larger the obstacle is compared to the wavelength, the less the waves will diffract

11  Interference  ability of two or more waves to combine & form a new wave  Waves pass thru each other & continue in original direction  New wave exists only while original waves are overlapping  Constructive interference  waves add together  Destructive interference  waves subtract from each other

12  Standing waves  a wave pattern that stays in one place  Form when waves of equal wavelength & amplitude that are traveling in opposite directions continuously interfere with each other  Nodes  the places where two waves always cancel each other  Resonance  ability of an object to vibrate by absorbing energy at its natural frequency


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