Waves and Electromagnetic Radiation Part 1

wave

disturbance that carries energy from one place to another

mechanical wave

a type of wave that carries energy through matter
- can be longitudinal or tranverse
- transferred through vibrating particles (solid, liquid or gas)

medium

the material or substance a wave moves through

longitudinal wave

a type of wave that transfers energy parallel to the direction of wave motion
- particles move horizontally with the wave

transverse wave

a type of wave that transfers energy perpendicular to the direction of wave motion - particles move up and down while the wave travels horizontally.

sound wave

a wave produced by the compression and expansion of an elastic medium in which it travles, such as air or water

• longitudinal

• so a medium is required

electromagnetic waves

a wave produced of electric and magnetic fields that radiates out from a source at the speed of light

• transverse

• energy is carried through space (visible light, mixrowaves, x-rays)

electromagnetic spectrum

the range of wavelengths and frequencies of electromagneti waves

• all waves on this spectrum are transverse

• a medium is not required

speed of light (edgenuity)

3 × 10^8 m/s

speed of sound (edgenuity)

3.31 × 10² m/s under standard temp/pressure

• depends on conditions of the medium

average velocity/speed

V = d/t

longitudinal wave examples

sound waves & earthquake P-waves

crest

highest point on a wave

trough

lowest point in a wave

wavelength

distance between any two equivalent points, such as from crest to crest or trough to trough, or for longitudinal from compression to compression or from rarefaction to rarefaction.

amplitude (transverse wave)

the height from the midpoint to the crest or the trough
- directly related to amount of energy in a wave
- higher —> higher energy, lower —> lower energy

compression

the part of a longitudinal wave where the particles of matter are close together

rarefaction

the part of a longitudinal wave where the particles of matter are far apart

amplitude (longitudinal)

how close together the particles in the medium are at compressions of the wave
- the closer the particles, the higher, the farther the particles, the lower

period

the amount of time it takes an object to complete a cycle or return to its original position (T)

(amount of time it takes one wavelength to pass a certain point)
unit seconds

frequency

number of oscillations per second (unit hertz)

frequency formula

cycles/time

formula relating period and frequency

T = 1/f

formula relating frequency and period

f = 1/T

velocity

the distance (wavelength) a wave travels in a given amount of time

formula for velocity, frequency, and wavelength

v= λ/T and v = fλ

relationship between frequency and wavelength

inverse

difference between electromagnetic & mechanical waves

first does not require a medium to carry energy, other one requires a medium to carry energy

why does media affect the speed of waves?

• light waves travel faster through gases and liquids

• soundw aves travel the fastest through solids and slowest through gases

• higher temperatures = particles bump into each other more often, increasing chance of energy transfer

absorption

occurs when matters in energy from a wave

• energy from the wave increases the internal energy of the object

transmission

the passing of a wave through an object

• energy is absorbed on one side of an object then reemited on the OTHER side

reflection

the bouncing of a wave off the boundary between two media
- energy is absorbed on one side and reemitted on the SAME side

refraction

bends a wave as it passes through one medium to another

• this can speed up or slow down the wave, depending on the properties of the medium

diffraction

bends and scatters waves as they hit an object or go through an opening

• this changes the direction of the wave and spreads out the energy

interference

occurs when two waves meet while traveling along the same medium

• can build on eachother or break eachother down

constructive interference

occurs when two interfering waves have a displacement in the same direction

• the resulting wave has a greater amplitude and more energy

destructive interference

occurs when two interfering waves have a displacement in the opposite direction

• the resulting wave has a lower amplitude and less energy

process of sound wave

1. starts when something is caused to vibrate (ex. a bell vibrates when struck)

2. energy from a vibrating object is transferred through the movement of particles within the medium, creating a mechanical wave

3. when a vibration in the medium strieks your ear, you hear the sound

4. after a sound is produced, it travels to teh ear through a medium

5. sound waves eventually dissipate

dissipate

each time the particles of the medium interact, part of the energy of the wave is lost

• the energy carried by the wave cannot be distinguished from other background movements of the medium

wavelength of sound waves

distance between any two equivalent point s

• in a sound wave, can be measured bewteen compressions or rarefractions

• measured in meters

pitch

determined by frequency of a suond wave (how high or low a sound is)

• directly proportional to frequency, inversely proportional to wavelength

amplitude (sound wave)

the density of the medium’s particles at the compressions of the wave

• determines loudness

• high-amplitude waves create louder sounds

• low-amplitude waves create softer sounds

wave speed

measures how fast the sound wave is traveling through a medium

• v = d/t

• v = fλ

type of medium (sound waves)

• fastest in solids, slowest in gases

• particles of solids —> close together —> higher chance of energy transfer

• particles of gases —> farther apart —> lower chance of energy transfer

temp of medium (sound waves)

• as temperature increases, particles of the medium move faster

• faster particles move, the greater chance the particles will bump into each other

• the more particles bump into eachother, the more energy is transferred

analog signals

continuous signals (ex. smart phones, records music in its original form)

digital signals

broken up into binary code (AM/FM radio)

quantization error

converting a continuous analog signal to a series of 1s and 0s introducing small errors to the sound as it is recorded

types of stresses on Earth’s surface

tension, compression, shearing

tension

type of stress that occurs when plates move apart

• rocks stretch apart

• stretching causes rocks to become thin in the middle

• occurs at divergent boundaries

normal fault

caused by tension

• plates are moving apart from the fault

• hanging wall lies above the fault

• footwall lives below the fault

• the hanging wall moves downward at this fault

compression

type of stress that occurs when one plate pushes against another

• rocks squeze together until they fold and break

• compression often occurs at convergent boundaries

reverse fault

caused by compression

• plates are moving toward the fault, colliding into one another

• hanging wall oves up, sliding over the footwall

shearing

type of stress when a rock mass is pushed in opposite directions

• rocks break and slip apart

• rocks change shape

• shearing is common at transform boundaries

strike-slip fault

occurs in areas of shearing

• plates slide past eachother in opposite directions

• plates have very little or no vertical movement

sedimentary basins

depressed or low areas in Earth’s crust

• areas where sediments are deposited

• formed through the movement of tectonic plates

rift basins

two plates seperate and Earth’s crust is stretched as a result

• plates move apart at divergent boundaries to form these

• weaker crust moves down at normal faults

wedge/arc basins

where the two plates collide, a wedge is formed at reverse faults.

• sediments are deposited on the wedge

the meeting of the plates compresses the oceanic crust, forming a volcanic island __

• basins can be formed at the fore__ and back___ regions

strike-slip basins

when bent or curved plates move past eachother, a depression is formed

• sediments are deposited in the depression

importance of sedimentary basins

• tell us about Earth’s history

• rocks contain valuable resources such as gemstones, precious metals, and fossil fuels

anticline

a fold in a rock that bends upward in an arch

syncline

a fold in a rock that bends downward

fault-block mountains

created when the hanging walls from parallel faults slip down

• created by parallel normal faults

plateau

when a large flat block of rock is pushed upward

• may contain many flat layers and is wider than it is tall

earthquake

is the shaking that results from movement under Earht’s surface

• caused by forces of plate movement

process of earthquake forming

1. plate movement causes stress

2. stress increases along faults

3. excess stress leads to rocks breaking, and an earthquake starting

focus

the area beneath the surface where rocks break under stress

• the starting point of an earthquake

epicenter

point on the surface directly above the focus

wave (earthquake)

earthquakes produce vibrations that arry energy as they travel

• seismic _____

P Waves (primary)

• arrive first

• travel the fastest

• compress and expand the ground like an accordion

• travel through solids and liquids

S Waves (secondary)

• arrive after P waves

• vibrate from side to side and up and down

• shake structures violently

• travel only through solids

Surface Waves

• travel only on the surface

• occur after P and S waves

• move slowly

• can produce dramatic ground movement

Mercalli scale

rates an earthquake according to how much damage it can cause

Richter scale

measures magnitude based on the size of seismic waves

• determined by measuring waves and fault movement

seismic wave (measurements)

• measured by a seismograph

• useful for measuring small, nearby earthquakes

moment magnitude scale

estimates total energy released by an earthquake

• useful for all earthquakes (all sizes & distances)

• data collected with seismographs

• shows what kind of seismic waves were produced and their strength

How to geologist locate an earthquake’s epicenter?

• use a seismograph to measure difference between arrival of P and S waves

• compare data to seismographs around the world

Sumatra Earthqauke

• 2004

• THIRD strongest earthquake ever recorded

• 9.1-9.3 on moment magnitude scale

• Maximum intensity on Mercalli Scale

• Approx. 9 minutes, longest ever measured

• Triggered massive tsunami

• Killed 250,000+ people