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Sound and Waves Introduction

Sound and Waves Introduction. Physical Science. Mechanical Wave. Mechanical waves require a medium Examples: shaking a rope or string, ocean tides, slinky and spring, diffusion of heat, etc. Waves carry energy from one location to another. Types of Mechanical Waves. Three types

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Sound and Waves Introduction

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  1. Sound and Waves Introduction Physical Science

  2. Mechanical Wave • Mechanical waves require a medium • Examples: shaking a rope or string, ocean tides, slinky and spring, diffusion of heat, etc. • Waves carry energy from one location to another

  3. Types of Mechanical Waves • Three types • Transverse Waves • Longitudinal Waves • Surface Waves

  4. Transverse Waves • Particles vibrate perpendicular of the direction the wave travels. • Trough is the lowest point and crest is the highest point. • Examples: A shaken string; electromagnetic radiation, radio waves, cell phone signals; AC current; etc.

  5. Longitudinal Waves • Particles vibrate in the direction of propagation! • Experiences compression: the area where the particles are most close together and rarefaction: the area where the particles are most distance from one another. • Examples: Sound waves, can be made on slinky, air cannons, etc.

  6. Surface Waves • A surface wave travels along a surface that separates two medium.

  7. Wave Properties • Period (T) – The time required to complete one cycle for a wave. Units are in seconds. • Frequency (f) – The number of complete cycles in a give time. Units of f are in Hertz (Hz). AKA inverse seconds 1/s • This means T=1/f and f=1/T

  8. Wave Length! • Wavelength (λ) is the distance between crest or toughs for transverse waves and the distance between compressions or rarefactions for longitudinal. • Lambda is how your pronounce λ • Wave length units are meters

  9. Wave Speed!!!!!! • Wave speed is equal to wave length times frequency that is V= λ x f • or if you hate λwave speed = frequency x wave length • Wave speed has units of meters per second (m/s) • The speed of light is always c however!

  10. Amplitude • This is how “big” the wave is or rather how large the displacement of the wave is from the origin.

  11. Behavior of waves • So very many properties. • Reflection, Refraction, diffraction, interference, standing waves

  12. Reflection • Reflection occurs when a wave bounces off a surface/barrier it is on able to pass through. • The speed and frequency of the wave does not change during a reflection.

  13. Refraction • Refraction occurs when the wave enters a new medium at an angle and changes direction. • Wave speed does change upon entering a new medium • This is how rainbows are created and how ocean waves change direction.

  14. Diffraction • Diffraction is the bending of a wave through or around an obstacle. • This is an important property of light and is often used in quantum mechanics.

  15. Interference!!!!!!!!!!!oneone1!!11! • This is an extremely important property of waves! • There are two types: constructive and destructive • Constructive and destructive interference are both examples of the superposition. • Superposition is how sound canceling headphones work, amplifiers, musical instruments (via the formation of standing waves • There is no music without superposition!

  16. Constructive Interference • Two like waves combine to have there amplitudes add forming an over all larger amplitude wave. • For sound, this makes the sound louder!

  17. Destructive Interference • Two waves combine to make a smaller amplitude wave. • This makes sound more quite and is how sound canceling head phones work!

  18. Standing Wave • Standing waves only form if multiple half of wavelengths fit into the length of a vibrating cord or string. • They have nodes and antinodes • Nodes are at a location of zero displacement • Antinodes are at the highest points of the wave

  19. Sound waves • Sound, is again, a longitudinal wave! • Sound travels at about 343 m/s at room temperature

  20. Decibels • The louder a sound is the higher its intensity • Larger intensities mean higher decibels • A rock concert is often at the threshold of pain and you will lose hearing with out protection

  21. Pitch and Frequency • A pitch is the frequency of sound as you perceive it. • High frequencies yield a high pitch and low frequencies a low pitch • Middle C has a frequency of 261 Hz, while an F# has a frequency of about 370 Hz. Well for first harmonics anyways.

  22. Doopppplllllleeeeeeerrrrrrrrrrrrrr • The Doppler effect is the change in frequency of a sound caused by the motion of the listener and/or source. • This effect also affects light from distance stars and is known as red/blue shifted light. • http://www.youtube.com/watch?v=Y5KaeCZ_AaY

  23. Electromagnetic Waves! • AKA light and much more! • Electromagnetic waves are created from accelerating electrons. • Electromagnetic waves can travel through a vacuum and matter. This means an electromagnetic wave require no medium to travel!

  24. Electromagnetic Wave Speed • All electromagnetic waves travel at c, the speed of light in a vacuum. • Also, Electromagnetic is often abbreviated as EM.

  25. EM frequency • Electromagnetic waves can vary in wavelength and frequency • Again v = f x λ • However, v = c for EM waves unless otherwise stated.

  26. EM Waves Behavior • EM waves behave very peculiar, they behave both like waves and particles. • This is known as wave particle duality and was discovered by Albert Einstein during his studying of the photoelectric effect. • EM energy is carried by little particles called photons and a photons energy is dependent on a waves frequency.

  27. Wave Spectrum!!! • EM waves come in all sorts of variety and are not just limited to visible light.

  28. Radio Waves • Includes both FM (frequency modulated) and AM (amplitude modulated) wavelength • Also includes: TV’s

  29. Microwaves • Includes microwaves (hopefully obviously) • Microwaves work by hitting the dipole moments in fats and water stored in food producing thermal energy • Also includes: radar

  30. Infrared Waves • Infrared is the wave length of light are bodies give off and most objects produce. • Infrared light is also used in TV remotes • Some infrared light can be seen by your cell phones camera!

  31. Visible Light • This is the ROY G. BIV we see from a rainbow and is the light we can see.

  32. Ultraviolet Waves • This is the invisible light produced by the sun responsible for sun burns! • It can kill a large amount of germs and bacteria and is often used for medical sterilization

  33. X-Rays • X rays have very short wave lengths and have a high energy • They can penetrate a large amount of matter and are often used in medical applications

  34. Gamma Rays • The highest frequency waves possible. • These waves can slice through cell membranes and damage your DNA possibly causing cancer • It is also used to treat cancer however, by destroying the cancer cells!

  35. Video of light colors! • If theres time • http://www.youtube.com/watch?v=S9dqJRyk0YM

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