Crave the Wave
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In Crave the Wave, participants will demonstrate knowledge and process skills needed to solve problems and answer questions regarding all types and areas of waves and wave motion. A calculator is required for this event.
Contents
Regionals Topics
 General Wave characteristics
 Wave Types
 Wave Phenomena
 Electromagnetic Waves Insert info on: energy carried (AM/FM only), standard wavelength bands, their uses and dangers, how the electromagnetic spectrum relates to everyday life, and mechanical and electromagnetic waves.
 Spectroscopy: Filters and Primary colors
Some calculations are required, such as calculation of frequency, period, wavelength, and speed.
Wave Characteristics
Types of Waves
The two main types of waves are longitudinal (An example of this could be a Pwave) and transverse (An example of this could be a Swave). Transverse waves propagate perpendicular to the direction of the wave. Longitudinal waves move parallel to the direction of the wave. These two wave types can be modeled with a Slinky. Start by having two people stretch a Slinky. To model a transverse wave, have one person shake their end of the Slinky with an upanddown or a righttoleft motion. To model a longitudinal wave, keep the Slinky completely straight and have one person quickly push their end of the Slinky to the other person.
Other types of waves include surface waves and torsional waves. Surface waves are waves that travel along the boundary of two media. The particles in a surface wave move in a circular motion. Torsional waves twist and spin. It is like a screw being drilled, or moving your arms back and forth while keeping them flat.
Transverse Waves
The main parts of a transverse wave are the crest, trough, wavelength, and amplitude. Also, there are additional characteristics of waves, such as frequency and period.
 Crest the highest point of a wave. Also called peak.
 Trough the lowest point of a wave.
 Rest position the position the wave would be in if there were no disturbances along it. Also called normal position and equilibrium position.
 Wavelength the distance between two crests or troughs. Measured by distance units of the metric system.
 Amplitude the distance between a crest or trough and the rest position. Measured by distance units of the metric system.
 Frequency the number of wavelengths passed per second. Measured in Hertz (Hz).
 Period the time a wave takes to complete a wavelength. Measured in seconds.
 Direction of Motion the direction in which the wave moves
 Direction of Oscillation the direction in which particles in the wave move, perpendicular to the direction of motion
 Velocity the speed and direction in which the wave is moving, equal to wavelength times frequency
Some of these parts are shown in the picture below:
Longitudinal Waves
 Compression the most compressed point of a wave
 Rarefaction the least compressed point of a wave
 Rest Position the position the wave would be in if there were no disturbances along it. Also called normal position and equilibrium position.
 Wavelength distance between two compressions or rarefactions. Measured by distance units of the metric system.
 Frequency the number of wavelengths passed per second. Measured in Hertz (Hz).
 Period the time a wave takes to complete a wavelength. Measured in seconds.
 Direction of Motion the direction in which the wave moves
 Direction of Oscillation the direction in which particles in the wave move, parallel to the direction of motion
 Velocity the speed and direction in which the wave is moving, equal to wavelength times frequency
Surface Waves
 Crest the highest point of a wave. Also called peak.
 Trough the lowest point of a wave
 Rest Position the position the wave would be in if there were no disturbances along it. Also called normal position, equilibrium position, and stillwater position
 Wavelength distance between two crests or troughs. Measured by distance units of the metric system.
 Frequency the number of wavelengths passed per second. Measured in Hertz (Hz).
 Period the time a wave takes to complete a wavelength. Measured in seconds.
 Direction of Motion the direction in which the wave moves
 Direction of Oscillation the direction in which particles in the wave move, circular motion
 Wave Height the vertical distance between a crest and a trough
 Velocity the speed and direction in which the wave is moving, equal to wavelength times frequency
Torsional Waves
 Direction of Motion the direction in which the wave moves
 Velocity the speed and direction in which the wave is moving
 Direction of Oscillation the direction in which particles of the wave move
Electromagnetic Spectrum
The electromagnetic field is a combination of the magnetic field and the electric field. All EM waves are transverse in nature. They all travel at the speed of light, [math]c = 3.00 \times 10^8 \frac{m}{s}[/math]. That means [math]\lambda \propto \frac{1}{f}[/math], as [math]v = \lambda f[/math] and [math]v = 3.00 \times 10^8 \frac{m}{s}[/math]. The photon energy of a wave is measured in joules and electron volts and can be calculated as follows: [math]e = hf = \frac{ch}{\lambda}[/math] where h = Planck's constant = [math]6.62607 \times 10^{34} Js[/math]. Radio waves are the waves with the least energy, longest wavelength, and smallest frequency. These can be split up into AM waves, FM waves, short radio waves, telemetry/millimeterwaves, and terahertz waves. Next are microwaves which are used in microwaves to heat food and infrared waves which humans emit. After that are visible light waves which things like lava emit. Ultraviolet rays are next. Then come xrays and gamma rays which have the highest energies.
Spectroscopy
This section is incomplete. It does not cover all aspects of this subject. Please keep this in mind when reading the page and add relevant information if possible. 
Colors
The primary colors of light are red, green, and blue, and the secondary colors of light are yellow, cyan, and magenta. Conversely, the primary colors of pigments are yellow, cyan, and magenta, and the secondary colors of pigments are red, green, and blue.
Filters
Filters: absorptive and dichroic/interference/thin film/reflective
Absorptive filters are usually made of glass with several compounds added which absorb specific wavelengths of light. They can also be made of plastic, which the compounds are added to, to produce gel filters.
Dichroic filters have little reflective cavities which resonate with specific wavelengths. Using destructive interference, the wavelengths are canceled out, leaving the rest of the wavelengths to pass through. They are used for precise scientific work since their exact color range can be controlled. Interference filters are more expensive and more delicate.
LongPass Filter: Transmits waves with wavelengths longer than a specific range, Attenuates waves with shorter wavelengths
ShortPass Filter: Transmits waves with wavelengths shorter than a specific range, Attenuates waves with longer wavelengths
BandpassFilter: Combination of longpass and shortpass filters, transmits waves with a wavelength in a specific interval
Monochromatic Filter: Only a small range (usually one color) of wavelengths is allowed to pass.
Infrared Filter: The term can refer to infraredpassing or infrared cutoff filters, infrared photography (passing), projectors (cutoff),
Ultraviolet Filter: Block ultraviolet rays but transmit visible light rays, ultraviolet pass and ultraviolet bandpass filters are much less common, used in cameras
Neutral Density Filter: Attenuate all wavelengths of visible light, optical density is the common logarithm of the transmission coefficient, which is [math]amplitude_{initial}:amplitude_{incident}[/math] or [math]intensity_{initial}:intensity_{incident}[/math], make photographic exposures longer
Polarizer Filter: Blocks light depending on its polarization, usually made of Polaroid, sunglasses and photography, darker color
Spectra
Absorption
Absorption spectra are the little bits of incident radiation absorbed by the material. They are helpful in chemical analysis of stars (determining what they are made of and what quantity). Here is an example absorption spectrum.
Emission
Emission spectra are the photons emitted from a material when electrons from the atom are excited (e.g., from being heated). They are helpful in determining the composition of stars. Here is an example emission spectrum.
Wave Phenomena
Interference
Two waves strike each other.
Constructive
The two waves reinforce each other.
Destructive
The two waves cancel out each other.
Doppler Effect
The Doppler Effect is a difference in the frequency of a wave caused by a source moving relative to the observer. The Doppler Effect occurs because when an object emitting a wave is moving, the crests of the wave will bunch up in front of the object and the crests of the wave will be more spread out behind it. This causes a higher frequency of a wave when its source moves towards the observer and a lower frequency of a wave when its source moves away from the observer. An example of this is a siren passing by. It will sound higher pitched as it approaches, but then sound lower after it passes. The following equation is used to calculate the frequency of a wave using the Doppler effect: [math]f=\left (\frac{c+v_r}{c+v_s} \right )f_0[/math]. [math]f[/math] is the observed frequency, [math]f_0[/math] is the emitted frequency, [math]c[/math] is the wave's velocity in the medium, [math]v_r[/math] is the velocity of the observer relative to the medium, it is positive when the observer moves towards the source and vice versa, [math]v_s[/math] is the velocity of the source relative to the medium, it is positive when the source moves away from the observer and vice versa.
Standing Waves
Standing waves are when a wave does not appear to be made up of moving waves. This is from a combination of reflection and interference. Nodes are points of maximum destructive interference while antinodes are points of maximum constructive interference.
The animation below shows the standing wave in pink, the initial wave in yellow, and the reflected beam in cyan (dotted):
Reflection
The change of direction so that the wave bounces off into the same medium in which it originated.
Specular
If the reflection interface is very smooth, specular reflection will occur. Specular reflection is mirrorlike (forms images).
Laws of reflection:
The normal, incident ray, and reflected ray all lie on the same plane.
The incident ray is the same angle from the normal as the reflected ray: [math]\theta_i = \theta_r[/math]
The incident ray and reflected ray are on opposite sides on the normal.
An image in a glass mirror is 1)virtual, 2)reversed, 3)the right side up, 4)the same size of the object, and 5)the same distance behind the mirror as the object is in front of the mirror.
Diffuse
If the reflection interface is rough (nonmetallic), diffuse reflection will occur. Diffuse reflection is where an incident ray is reflected at many different angles as opposed to specular reflection with only one angle of reflection. The visibility of objects is primarily due to diffuse reflection. Diffuse interreflection occurs when light reflected off a nearby object reflects off surrounding objects, illuminating them.
Refraction
Refraction is the change in direction of a wave caused by a change in its medium. Refraction is responsible for rainbows and mirages.
Snell's Law
The index of refraction, also called refractive index, is a measure of how light refracts in a medium. Its formula is [math]n=\frac{c}{v}[/math]. n is the refractive index, c is the speed of light in a vacuum, and v is the speed of light in that medium.
Snell's Law states that the ratio of the velocities of a wave in two media is equal to the ratio of the sine of the angles of incidence, which is also equal to the reciprocal of the ratio of the refractive indices. The formula is [math]\frac{\sin \theta_1}{\sin \theta_2}=\frac{v_1}{v_2}=\frac{n_2}{n_1}[/math]. [math]\theta[/math] is the angle of incidence/reflection, which is measured from the normal, v is the velocity out of/in the medium, and n is the refractive index. Angles are measured from the normal.
Apparent Depth
When refraction occurs, velocity changes and frequency remains the same, so the wavelength of the wave must change because [math]v=\lambda f[/math]. In general, the wave is partially reflected and partially refracted. The ratio of real depth to apparent depth is the ratio of the refractive index of water to that of air.
Kerr and Pockels Effects
The Kerr Effect is the change of refractive index of a material because of an applied electric field. [math]\Delta n \propto E^2[/math], meaning the change in the refractive index is proportional to the square of the energy of the electric field. The Kerr ElectroOptic Effect, or DC Kerr Effect, is when a slow varying electric field is applied. This makes the material birefringent, meaning the material shows different indices of radiation for light polarized parallel and perpendicular to the electric field. The difference is shown by the equation [math]\Delta n = \lambda KE^2[/math] where [math]\Delta n[/math] is the change in the index of reflection, [math]\lambda[/math] is the wavelength of light, K is the Kerr Constant for the material, and E is the energy of the electric field. The Optical Kerr Effect, or AC Kerr Effect, is when the electric field is due to the light itself. The MagnetoOptic Kerr Effect is when light reflected from a magnetized object has a slightly rotated plane of polarization.
The Pockels Effect is the change of refractive index of a crystal that does not show inversion symmetry, such as lithium niobate and gallium arsenide, because of an applied electric field. It differs from the Kerr effect in that [math]\Delta n \propto E[/math], meaning the change in the refractive index is linear instead of quadratic.
Refractive Indices
Material  Refractive Index 

Vacuum  1 
Gases at 0°C and 1 atm  
Air  1.000293 
Carbon Dioxide  1.00045 
Helium  1.000036 
Hydrogen  1.000132 
Liquids at 20°C  
Arsenic Trisulfide and Sulfur in Methylene Iodide  1.9 
Benzene  1.501 
Carbon Disulfide  1.628 
Carbon Trichloride  1.461 
Ethyl Alcohol (Ethanol)  1.361 
Silicone Oil  1.3361.582 
Water  1.3330 
10% Glucose Solution in Water  1.3477 
20% Glucose Solution in Water  1.3635 
60% Glucose Solution in Water  1.4394 
Solids at Room Temperature  
Titanium Dioxide (Rutile Phase)  2.614 
Diamond  2.419 
Strontium Titanate  2.41 
Amber  1.55 
Fused Silica (Fused Quartz)  1.458 
Sodium Chloride  1.544 
Other  
Liquid Helium  1.025 
Water Ice  1.31 
Cornea (human)  1.3731.401 
Lens (human)  1.3861.406 
Acetone  1.36 
Ethanol  1.36 
Glycerol  1.4729 
Bromine  1.661 
Teflon AF  1.315 
Teflon  1.351.38 
Cytop  1.34 
Sylgard 184 (Polydimethylsiloxane)  1.4118 
Polylactic acid  1.46 
Acrylic glass  1.490  1.492 
Polycarbonate  1.584  1.586 
PMMA  1.4893  1.4899 
PETg  1.57 
PET  1.5750 
Kerosene  1.39 
Crown glass (pure)  1.50  1.54 
Flint glass (pure)  1.60  1.62 
Crown glass (impure)  1.485  1.755 
Flint glass (impure)  1.523  1.925 
Pyrex (a borosilicate glass)  1.470 
Cryolite  1.338 
Rock salt  1.516 
Sapphire  1.762–1.778 
Sugar Solution, 25%  1.3723 
Sugar Solution, 50%  1.4200 
Cubic zirconia  2.15  2.18 
Potassium niobate ([math]KNbO_3[/math])  2.28 
Silicon carbide  2.65  2.69 
Cinnabar (Mercury sulfide)  3.02 
Gallium(III) phosphide  3.5 
Gallium(III) arsenide  3.927 
Zinc Oxide  2.4 
Germanium  4.05  4.01 
Silicon  3.48  3.42 
Diffraction
Diffraction is when a wave spreads out when encountering a corner or hole, such as a doorway or slit, that is comparable to its wavelength. Francesco Maria Grimaldi, and Italian scientist, coined the word 'diffraction.' Diffraction is described by the HuygensFresnel Principle.
State Topics
At States you will also need to demonstrate your knowledge about seismic waves.
Seismic Waves
This section is incomplete. It does not cover all aspects of this subject. Please keep this in mind when reading the page and add relevant information if possible. 
There are 5 major earthquake waves:
 Pwaves aka primary waves, are longitudinal waves. They are the first to arrive. They can travel through liquids.
 Swaves aka secondary or shear waves, are transverse waves. They are second to arrive. They cannot travel through liquids.
 Surface Waves combinations of P and S waves and occur on the surface. They are the slowest waves.
 Rayleigh Waves waves that roll in an oceanlike motion.
 Love Waves waves that move in side to side, horizontally. Love waves cause the most damage.
National Topics
In addition to the Regional and State topics, Nationals will introduce Breaking ocean waves and Tsunamis.
Breaking Ocean Waves
This section is incomplete. It does not cover all aspects of this subject. Please keep this in mind when reading the page and add relevant information if possible. 
Tsunamis
A tsunami, or seismic sea wave, is a series of ocean waves that can be caused by things such as earthquakes or volcanic activity.
Notable Tsunamis
The earthquake and tsunami in the Indian Ocean on December 26, 2004, was the most devastating tsunami ever recorded. The estimated amount of casualties was 280,000 people.
Japan has a history of tsunamis, but a recent one was the earthquake of the coast of Japan on March 11, 2011. The tsunami is probably most known for the three nuclear reactors at the Fukushima plant that had meltdowns, causing the meltdown to be declared the largest nuclear disaster since Chernobyl.
Equations to Know
This section is incomplete. It does not cover all aspects of this subject. Please keep this in mind when reading the page and add relevant information if possible. 
There are several helpful formulas and equations to know.
 Frequency and Period
 [math]f=1/T[/math]
 Rates
 [math]r=d/t[/math]
 Velocity
 [math]v=\lambda f[/math]
 Snell's Law
 [math]\sin \theta_1 / \sin \theta_2=v_1 / v_2 = n_2 / n_1[/math]
 Rayleigh criterion
 Young's Equation
 Gratings
 Harmonics and Resonant Frequency
 [math]f_n = (n + 1) * f_0[/math]
 Polarization
 Brewster's Angle
 Energy of a Photon
 [math]e=hf=ch/\lambda[/math]
 Dimensional Analysis
 Wavelength of Colors
Sample Questions
 If the frequency of a light wave is 2 Hz (2 cycles per second), what is the wavelength?
 If the wavelength of a sound wave through air at 20 degrees Celsius is 2 cm, what is the frequency in Hz (cycles per second)?
 If the period is 2 seconds, what is the Frequency?
 What is Destructive Interference?
 Which seismic wave is faster? Primary waves or Secondary waves?
 Given an image of a wave, identify the wavelength.