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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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mechanical wave
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
Types of Mechanical Waves
  • Three types
  • Transverse Waves
  • Longitudinal Waves
  • Surface Waves
transverse waves
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.
longitudinal waves
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.
surface waves
Surface Waves
  • A surface wave travels along a surface that separates two medium.
wave properties
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
wave length
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
wave speed
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!
  • This is how “big” the wave is or rather how large the displacement of the wave is from the origin.
behavior of waves
Behavior of waves
  • So very many properties.
  • Reflection, Refraction, diffraction, interference, standing waves
  • 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.
  • 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.
  • 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.
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!
constructive interference
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!
destructive interference
Destructive Interference
  • Two waves combine to make a smaller amplitude wave.
  • This makes sound more quite and is how sound canceling head phones work!
standing wave
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
sound waves
Sound waves
  • Sound, is again, a longitudinal wave!
  • Sound travels at about 343 m/s at room temperature
  • 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
pitch and frequency
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.
  • 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.
electromagnetic waves
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!
electromagnetic wave speed
Electromagnetic Wave Speed
  • All electromagnetic waves travel at c, the speed of light in a vacuum.
  • Also, Electromagnetic is often abbreviated as EM.
em frequency
EM frequency
  • Electromagnetic waves can vary in wavelength and frequency
  • Again v = f x λ
  • However, v = c for EM waves unless otherwise stated.
em waves behavior
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.
wave spectrum
Wave Spectrum!!!
  • EM waves come in all sorts of variety and are not just limited to visible light.
radio waves
Radio Waves
  • Includes both FM (frequency modulated) and AM (amplitude modulated) wavelength
  • Also includes: TV’s
  • Includes microwaves (hopefully obviously)
  • Microwaves work by hitting the dipole moments in fats and water stored in food producing thermal energy
  • Also includes: radar
infrared waves
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!
visible light
Visible Light
  • This is the ROY G. BIV we see from a rainbow and is the light we can see.
ultraviolet waves
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
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
gamma rays
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!
video of light colors
Video of light colors!
  • If theres time