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Waves Chapter 11

Waves. A repeating movement that transfers energy through space.Note that waves do not carry matter!!. Two types of waves:. TransverseMatter moves perpendicular to the medium.CompressionalMatter moves parallel to the medium.. Wave Parts (transverse). Crest: top of each waveTrough: bottom of ea

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Waves Chapter 11

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    1. Waves Chapter 11

    2. Waves A repeating movement that transfers energy through space. Note that waves do not carry matter!!

    3. Two types of waves: Transverse Matter moves perpendicular to the medium. Compressional Matter moves parallel to the medium.

    4. Wave Parts (transverse) Crest: top of each wave Trough: bottom of each wave Rest position: center of each wave Amplitude: crest to rest -or- trough to rest. Wavelength (?): Crest to crest -or- trough to trough.

    5. Wave parts (compressional) Rarefaction: less dense area (spread out part) Compression: More dense area (squeezed together part) Wavelength (?): One compression and one rarefaction Amplitude: amount of compression

    6. Wave frequency Symbolized in equation by (ƒ) Defined as the number of full waves that pass by a given point in 1 second. A frequency of 1 Hz means that 1 wave passes by in 1 second.

    7. Wave velocity If you take the wavelength and multiply it by the frequency, it will tell you how fast the wave was moving… Formula: v= ? • ƒ Units: m/s=m • Hz

    8. Behavior of waves Reflection: When a wave strikes a surface and bounces back. Refraction: When a wave bends due to its velocity change as it passes from one medium to another (speed decreases as it travels into a denser material).

    9. Behavior of waves cont. Diffraction: Bending of a wave around an object. Different from refraction because in refraction the wave bends as it passes through something, not as it goes around it.

    10. Behavior of waves cont. Interference: When two or more waves meet at the same place they temporarily combine to form a new wave until they have passed each other. Two types: constructive (two crests meet and add together) and destructive (a crest meets a trough).

    11. Electromagnetic waves Review Questions: What surrounds a magnet? What surrounds an electric charge? What is the relationship between magnetism and electric charge? What makes a wave?

    12. Electromagnetic Waves Vibrating electrons make electric field, due to this motion of electric current there is a magnetic field around it. As the electric field changes back and forth it causes the magnetic field changes back and forth.

    13. Electromagnetic waves These types of waves do not require matter to transfer their energy. Energy carried by electromagnetic waves is called radiant energy.

    14. Sound vs. Light Race! Through empty space electromagnetic waves travel 300,000 km/s, called speed of light (slightly less in air). Sound travels 347m/s in air.

    15. Electromagnetic Spectrum

    16. Electromagnetic Spectrum The shorter the wavelength the more dangerous. Humans can only see a small part of the spectrum called the visible light spectrum.

    17. Radio Waves Longest wave, smallest frequency. Includes… Radio signals (AM/FM) Microwaves Radar MRI (magnetic resonance imaging)

    18. Infrared Thermal energy is transferred by infrared waves. Warmer objects emit more infrared waves. This is used in: household security systems. Military

    19. Visible light ROY G BIV A prism can be used to break white light up into its color spectrum. Longer wavelengths bend more than shorter.

    20. Ultraviolet waves Good yet bad… Helps body produce vitamin D UVA and UVB rays cause skin cancer Helps kill bacteria on food and medical supplies Ages the skin

    21. X-rays and Gamma rays Used to view bones, teeth, luggage, etc. Used to kill diseased cells such as cancer, etc.

    22. Sound Sound waves are compressional waves. Sound can travel through any medium, solid, liquid, or gas, but it must have particles to travel on. Sound cannot travel on the moon because of the lack of particles.

    23. Speed of Sound Sound travels slowest through a gas, faster through liquids, and fastest through solids. Due to the closeness of the particles. Louder does not travel faster. Also depends on temperature… warmer is faster because there are more collisions.

    24. Mini lab Passing the book though a “solid” vs. a “liquid” vs. a “gas”

    25. Characteristics of compressional waves Intensity- related to the energy of the wave. It affects how far the sound can be heard. Loudness- Human perception of sound intensity. Measured in decibels (dB).

    26. Characteristics of compressional waves cont. Pitch- How high or low a sound seems to be. It is related to the frequency. Higher pitch is faster frequency. Recall that frequency in sound waves is the number of compressions -or- rarefactions that pass a given point in one second.

    27. Characteristics of compressional waves cont. Ultrasonic waves- frequencies above 20,000 Hz- Humans cannot hear them (ex: medical diagnosis machines). Infrasonic waves- Frequencies below 20 Hz- to low for humans to hear but they can feel them (ex: wind).

    28. Doppler Effect Change in pitch or frequency due to a moving source. Rings demo?

    29. Music and Sound Overtone- A vibration whose frequency is a multiple of the fundamental wave. Resonator- Hollow chamber filled with air that amplifies sound. Acoustic- The study of sound.

    30. Echolocation Locating object’s by emitting sounds and interpreting the sound waves that are reflected back. Bats Sonar ultrasound

    31. Light Three ways that light reacts with matter: Absorb, reflects, or transmits. Opaque: All light is absorbed and/or reflected (none passes through). Translucent: Allows some light through but you can’t see clearly through the object. Transparent: Transmits almost all light (see through).

    32. Primary colors of light When you combine green, red and blue light (the three primary colors of light) they form white light. Primary colors of pigment: Magenta, cyan, yellow. When they are combined, they form black.

    33. Sight Cones: Allow you to see color and detail of shapes. Three types: red (responds to red and yellow), green (yellow and green), and blue (blue and violet). Rods: Sensitive to dim light and helpful for night vision. (after images demo)

    34. Reflection Occurs when light waves strike an object and bounce off.

    35. Law of reflection The angle at which light strikes a surface (angle of incidence) is equal to the angle at which it is reflected (angle of reflection).

    36. Refraction Caused by the change in speed of a wave when it passes from one medium to another. Index of refraction: How much a material reduces the speed of light…depends on the density of the material.

    37. Prisms Break up white light into the color spectrum. Natural prism: raindrops. (prism demo)

    38. Mirrors

    39. lenses

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