# Characteristics of Waves

Created 3 years ago

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Slide Content

• Chapter 20
2. ### Slide 2 - Waves and Energy

• Waves do not carry matter
• Waves carry energy
• Scientific definition: a traveling disturbance that carries energy from one place to another
3. ### Slide 3 - Where do waves get energy?

• Waves get their energy from a vibration
• An object that is vibrating is moving
• A moving object has energy
4. ### Slide 4 - What do waves travel through?

• Medium is the matter or substance a wave travels through
• Waves that require a medium are mechanical waves
• Waves that do not require a medium to travel through are called electromagnetic, they travel through a vacuum
5. ### Slide 5 - Characteristics of Waves

• All waves have amplitude, wavelength, and frequency
• Parts of a wave: crest and trough
6. ### Slide 6 - Amplitude

• When a wave moves from its resting place to the crest it is measuring its amplitude
• The amplitude of a wave indicates the amount of energy carried by the wave
7. ### Slide 7 - Wavelength

• The distance between two crests or two troughs
• Symbol is λ Greek letter lambda
8. ### Slide 8 - Frequency

• The number of complete waves per unit cycle
• Unit used is called Hertz for Heinrich Hertz who studied waves
• 1 hz = 1 wave/sec
9. ### Slide 9 - Transverse Waves

• A wave in which the motion of the medium is at right angles to the direction of the wave
10. ### Slide 10 - Longitudinal Waves

• A wave that consists of a series of compressions and rarefactions
• The motion of the medium is parallel to the direction of the wave
11. ### Slide 12 - Combinations of Waves

• Surface wave is the combination of both transverse and longitudinal waves
12. ### Slide 13 - Speed of Waves

• The speed of a wave is determined by the number of waves passing a point in a certain amount of time (frequency) and the length of the wave (λ)
• Speed = frequency * wavelength
• A wave with a frequency of 4 hertz and a λ of 2 meters has a speed of 8 m/sec
• The speed of a wave depend upon the medium through which it travels and it is always constant
13. ### Slide 14 - Interactions of Waves

• The four basic wave interactions are reflection, refraction, diffraction, and interference
14. ### Slide 15 - Reflection

• Is the bouncing back of a wave after it hits a boundary
• Law of Reflection states that the angle of incidence is equal to the angle of reflection
15. ### Slide 16 - Refraction

• The bending of waves due to the change in speed, this is due to the speed at which waves travel in different mediums
16. ### Slide 17 - Diffraction

• The bending of waves around the edge of an obstacle
• The amount of diffraction depends on the wavelength and the size of the obstacle
17. ### Slide 18 - Interference

• When 2 or more waves arrive at the same place at the same time they react in a process called interference. The waves combine to form a single wave
18. ### Slide 19 - Constructive Interference

• If the waves combine in a way to make that the disturbance that results is greater than either wave alone
19. ### Slide 20 - Destructive Interference

• If the waves combine in such a way that the disturbance that results is less than either wave alone
20. ### Slide 21 - Standing Waves

• A wave that does not appear to be moving
• The points on a standing wave where destructive interference results in no energy displacement are called nodes
• The points at which constructive interference causes maximum energy are called antinodes
21. ### Slide 23 - Resonance

• The frequency at which a standing wave occurs is called the natural frequency or resonant frequency.
• In real life, waves usually give a mishmash of constructive and destructive interference and quickly die out. However, at certain wavelengths standing waves form, resulting in resonance. These are waves that bounce back into themselves in a strengthening way, reaching maximum amplitude.

• Chapter 21
23. ### Slide 25 - How Sounds are Made

• Sounds are vibrations that travel in longitudinal waves
• A vibration is the complete back and forth motion of an object
• At the crest of each wave is a compression of the molecules of the medium
• At the trough is a rarefaction of the molecules of the medium
24. ### Slide 26 - Sound and Media

• Medium is the substance that the sound wave travels through
• Fastest in solids, then liquids, then gases.
• Why?
• Space is a vacuum, with no matter to carry the sound wave, so no sound is heard from space.
25. ### Slide 27

• Threshold of Hearing
• 0dB Normal Breathing
• 10dB Rustling Leaves
• 20dB
• 30dB Library
• 40dB
• 50dB Normal Conversation
• 60dB
• 70dB Noisy Office with machines
• 80dB Heavy Traffic
• 90dB
• 100dB Construction Noise (up close)
• 110dB
• Threshold of Pain
• 120dB Rock Concert
• 130dB
• 140dB Jet Takeoff (from runway)
• 150dB
26. ### Slide 28 - Human Hearing

• Infrasonic – sounds 0-20 hz to low for humans to hear
• Ultrasonic - sounds greater than 20,000 hz to high for humans to hear
• Most humans can hear 20-20,000 hz most of their lives.
27. ### Slide 29 - Hearing Loss and Deafness

• The most common type of hearing loss is called tinnitus, caused by exposure to loud sounds or music
• How to prevent it? Turn your I-pods down!!!!!!
• Protect your hearing by wearing ear protectors if you know you are going to be exposed to loud noise.
28. ### Slide 31 - Speed of Sound

• The speed of sound is determined by the temperature, elasticity, and density of the medium through which the sound travels
29. ### Slide 32 - Temperature

• Sound travels faster at higher temperatures and slower at lower temperatures due to the molecules of the medium
• Air at 0° 331 m/sec
• Air at 25° 346 m/sec
30. ### Slide 33 - Elasticity and Density

• Solids are more elastic than either liquids or gases, the medium returns to its original position ex. Running on pavement or sand
• Sound travels best in solids, then liquids, and worst in gases because the molecules are closer together in solids
31. ### Slide 34 - Frequency and Pitch

• The description of a sound as either high or low is its pitch
• The pitch depends on the frequency of a sound
• High frequency=high pitch low frequency=low pitch

33. ### Slide 36 - Doppler Effect

• The change in pitch due to the movement between the sound and the receiver
• Coming toward the receiver the sound waves are pushed together
• Moving away the sound waves have more space between them
34. ### Slide 37 - Intensity and Loudness

• Intensity determines the loudness of a sound
• Intensity is the amount of energy carried in a wave in a certain amount of time
• The larger the amplitude the greater the intensity of a wave
35. ### Slide 38 - Reflection of Sound Waves

• Reflection of sound waves is called an echo
• Echolocation
36. ### Slide 39 - Sonar

• High frequency ultra-sonic waves are used in a system called Sound Navigation And Ranging or sonar
37. ### Slide 40 - Ultrasounds

• Ultrasonic waves are directed into a body and the resulting picture can be seen from the deflected waves