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Chapter 15 WAVES. Waves Wave - a disturbance that transfers energy through matter or a medium.

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Presentation on theme: "Chapter 15 WAVES. Waves Wave - a disturbance that transfers energy through matter or a medium."— Presentation transcript:

1 Chapter 15 WAVES

2 Waves Wave - a disturbance that transfers energy through matter or a medium.

3 Waves - waves transfer energy -Most waves are caused by vibrating objects. dnv2xo9Ndw

4 Types of Waves a wave that requires a medium to travel through. 1. Mechanical wave - Ex. Sound, ocean waves,earthquake waves

5 Types of Waves a wave that does NOT require a medium to travel through. 2. Electromagnetic wave - Ex. - these pass though by magnetic fields or electromagnetic fields light

6 Wave Forms a wave that causes the particles to vibrate perpendicular to the direction the wave travels 1. Transverse waves - Ex. Stadium wave, radio waves, Heat waves,

7 Wave Forms a wave that causes the particles of the medium to vibrate parallel to the direction the wave travels. 2. Longitudinal waves - Ex. Sound wave, compression wave

8 Wave Forms – particles move both perpendicular and parallel to the direction in which the wave travels. 3. Surface waves - Ex.

9 Sound Wave – require a medium to travel through. Sound wave - - longitudinal waves - causes the particles of the medium to vibrate parallel to the direction the wave travels.

10 The distance between any one point on a wave to an identical point on next wave. Determines the type and color of the wave. Wave Properties Wavelength-

11 Wave Properties The top of a wave The bottom of a wave - trough- - crest

12 Half the distance from the crest and the trough. - determines the loudness of the sound. Amplitude Wave Properties

13 period - The time it takes a complete wavelength or wave oscillation to occur. - same distance as the wavelength.

14 Wave Properties frequency - How many waves created in a given time; the number of cycles or vibrations in a given time. - determines the pitch of the sound. - high frequency = high pitch. - SI label is Hertz (Hz)

15 Frequency wave

16 Wave Speed Wave speed (v)- the speed of a wave is equal to wavelength divided by period, or frequency multiplied by wavelength. Two ways you can find wave speed: - wave speed (v) = wavelength/period OR v = frequency x wavelength

17 Wave Speed Ex. Waves passing by a pier have a frequency of.5 Hz and a wavelength of 10 m. What is the wave speed?

18 Determinates of wave speed: -The medium determines the speed of the wave. Ex. Sound: travels fastest in solid ( x faster than air ) travels fast in liquid travels slowest in air (about 340 m/s) Ex. Light: travels fastest in empty space (c = 3 x10 8 m/s or 186,000 mi/s) slows down when it has to go through air or water

19 Determinates of wave speed: Kinetic energy explains this. In air, molecules are far apart and won’t hit one another quickly. In solids, they are very close and will easily hit (vibrate) one another.

20 Doppler Effect Doppler effect – an observed change in frequency of a wave when the source or observer is moving.

21 Doppler Effect As the ambulance is coming towards you, the siren sound is hitting you quicker, so the pitch is higher. As the ambulance is going away from you, the siren sound is going away, so it takes longer to hit your eardrum, so the pitch is lower. assignment-discovery-doppler-effect-video.htm

22 Wave Interactions What happens when a wave meets an object or another wave? –Waves can reflect, diffract, refract or interfere What happens when a wave meets an object or another wave? –Waves can reflect, diffract, refract or interfere

23 Reflection Reflection-The bouncing back of a wave when it meets a surface or boundary Examples: –Water waves reflect off the side of a boat –Light waves reflect off the surface of a lake Reflection-The bouncing back of a wave when it meets a surface or boundary Examples: –Water waves reflect off the side of a boat –Light waves reflect off the surface of a lake

24 Diffraction Diffraction-A change in the direction of a wave when the wave meets an obstacle (ex. An opening) Examples: – Sound waves diffract around corners –Water waves diffract around rocks Diffraction-A change in the direction of a wave when the wave meets an obstacle (ex. An opening) Examples: – Sound waves diffract around corners –Water waves diffract around rocks interference

25 Refraction Refraction -The bending of a wave when it passes between 2 mediums in which the speed of the wave differs Example: Straw in water Refraction -The bending of a wave when it passes between 2 mediums in which the speed of the wave differs Example: Straw in water

26 Interference Interference -The combination of 2 or more waves that result in a single wave

27 Interference Constructive interference -The combination of 2 or more waves that produce a wave with an increased amplitude Destructive interference -The combination of 2 or more waves that produce a wave with a decreased amplitude Constructive interference -The combination of 2 or more waves that produce a wave with an increased amplitude Destructive interference -The combination of 2 or more waves that produce a wave with a decreased amplitude

28 Interference

29 Interference: Sound Waves Interference of sound waves produce beats – Beats -A pattern of alternating loud and soft sounds Interference of sound waves produce beats – Beats -A pattern of alternating loud and soft sounds

30 Interference: Light Waves


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