Sound and waves introduction
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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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Sound and Waves Introduction

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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

  • Transverse Waves

  • Longitudinal Waves

  • Surface 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

  • 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

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

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!

  • 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 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

  • 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.


  • 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

  • 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

  • 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 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, 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

  • 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!

  • 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

  • All electromagnetic waves travel at c, the speed of light in a vacuum.

  • Also, Electromagnetic is often abbreviated as EM.

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 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!!!

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

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 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

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

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 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

  • 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!

  • If theres time


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