physics waves

mechanical waves

require a medium to propagate

electromagnetic wave

can propagate through a vacuum

medium

stuff vibrated by transfer of energy through a wave

p-waves get a speed boost through

solids

inner core if the earth is

a solid

sound waves are

longitudinal

outer core

is a liquid, blocks s-waves from passing to the other side of earth

transverse earthquake waves

reveal structure of earth’s interior

light waves are

transverse waves

water waves

involve a combination of both longitudinal and transverse motions

as a wave travels through water, the particles travel in

clockwise circles

a surface wave is sometimes referred to as a

circular wave

sound

a wave of pressure variation traveling through matter

light

a stream of massless particles, called photons, that vibrate in every direction perpendicular to the direction the energy is moving

light waves are

transverse and electromagnetic

sound waves are

longitudinal and mechanical

sound - pitch

• human range 20-20,000 Hz

• Infrasonic f<20 Hz

• Ultrasonic f>20,000 Hz

light - visible and invisible

• human range (4.3-7.5) x 10^14 Hz

• Visible light different colors

amplitude

intensity related to energy

light

measured in luz or candela

speed of sound depends on

temperature and state of matter

increase in air temp

increase speed of sound

sound is faster in

solids and liquids, than in air

reflect

change direction when bounce off a boundary

rigid boundary

the pulse is inverted after it bounces

non-rigid boundary

the pulse is upright after it bounces

refract

change in speed, direction, and wavelength between different media

doppler effect

apparently change in frequency detected based on the movement or source and/or of the observer

if source and observer move towards each other,

higher frequency is detected

if source and observer move away from each other,

lower frequency is detected

in the doppler effect, frequency of the source

remains constant

diffraction

change in direction of wave through opening or around a barrier

when diffracted waves interfere with each other, you get a

diffraction pattern

interference

when two or more waves occupy the same space at the same time

principles of superstition

the resulting displacement of the medium is the sum of the displacements due to each individual wave

constructive interference

if the waves are “in phase,” that is crests and troughs are aligned, the amplitude is increased

destructive interference

if the waves are “out phase",” that is crests and troughs are misaligned, the amplitude is decreased and can even be zero

Mercalli scale

measure the amount of damage done as a result of an earthquake

Richter scale

measures the amplitude if the seismic waves and correlates that to the amount of energy released on a logarithmic scale

Moment magnitude

measures plate displacement and force involved in movement of the plate and correlates that to the amount of enegy released

ocean waves are

surface waves

sonic booms

• continuous front of high pressure generated by faster than sound sources

• constructive interference in our ears when sound of source is faster than speed of sound

beats

loud-soft pattern that characterizes two nearly (but not exactly) matched frequencies

resonance

occurs when a vibration from one oscillator occurs at a natural frequency for another oscillator

resonance cause

an increase in amplitude of wave

fundamental frequency

• lowest frequency in which resonance occurs

• lowest frequency of a periodic waveform

• in music- first harmonic

resonance run amuk

if the force that caused the resonance persists, dramatic and sometimes drastic things can occur

standing waves

when two waves occupy the same space at the same time

nodes are

points where there is no displacement of the medium

antinodes are

points where there is a maximum displacement of the medium

musical instruments are

standing waves

strings

• nodes at both ends (string is fixed on both ends)

• wavelength = 2L

open pipe

antinodes at both ends because tube is open on both ends

• wavelength = 2L

close pipe

antinode at one end and a node at the closed end

• wavelength = 4L

earthquakes

more commonly along fault lines

fault

a fracture in the rocks that make up the earth’s crust

earthquakes are caused by sudden motions along

faults

epicenter

the point at the surface of the earth directly above the focus

focus (hypocenter)

the point within the earth where an earthquake rupture starts

plates

massive rock that make up the outer layer of the earth’s surface, and whose movement along faults triggers earthquakes

seismic waves

waves that transmit energy released by an earthquake

most active faults are located

at or near plate boundaries

elastic rebound theory

explains why we have movement along a fault

san andreas fault

plates grind past each other

focus is the

origin if the earthquake

epicenter is

the spot on the surface of the earth directly above the focus

p-waves ____ and create a ____

refract, shadow zone

refraction can only happen with

different layers

s waves are _____ by the _____

absorbed, liquid outer core

p waves that go through the center of earth arrive ____ than those that do not

faster

seismograph

instrument that detects and records seismic waves

seismogram

record produced by seismograph

scientists measure the strength and chart the location of earthquakes using

seismic waves

magnitude

measure if energy released by an earthquake

On a Richter scale, each level is __ times stronger than the previous

10

Mw =

moment magnitude

ML (local) (eg Richter scale)

based on the amplitude of waves with 1s period within 600 km of epicenter