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# What does the doppler effect mean? Description

##### Description: concepts week 8 notes
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Week 8

## What does the doppler effect mean?

2/29/16

A wave having a frequency of 10 Hz means which of the following? 1 wave  goes up and down 10 times every second

∙ The Two Kinds of Waves:

o Transverse

 Motion is perpendicular to wave direction

o Longitudinal

 Motion is same direction as wave

A long, taut string on a guitar is plucked. The wave that travel down its  length is: transverse

∙ Technology

o Amplitude Modulated (AM)

o Frequency Modulated (FM)

∙ Which of the following is an observation we can make about pipes in a  pipe organ?

## What does the transmission mean?

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o The length of the pipe is inversely proportional to the frequency  of the sound it produces

∙ Interference

 If you have 2 different waves, each 1 inch, and the crests  of the waves move together, the result is a 2-inch wave We also discuss several other topics like What is the meaning of tax advantages?

 Act together

o Destructive Interference—subtractive

 If crest of one wave lines up with trough of another wave,  the result is 0 amplitude

 Cancellation

∙ The Electromagnetic Wave

o Maxwell

 Light is a wave of electromagnetic field

 Electromagnetic waves change, which creates another

electromagnetic wave which changes, and creates another  electromagnetic wave, etc.

## What does absorption mean?

o Michelson

 There are mediums that let waves propagate

 Light has no medium

∙ The Anatomy of the Electromagnetic Wave

o Point A—maximum strength but decreasing

o Point B—minimum strength but increasing

o Electromagnetic waves continue through internal mechanisms  and transfer energy as they travel

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∙ Light and the Energy of Electromagnetic Waves

o Speed of light

 All electromagnetic waves have same velocity

 c = 30,000 km/s

o Energy

 Higher frequency = blue color

 Lower frequency = red color

∙ Doppler Effect

o Wave motion is independent of its source

o If source moves, frequency appears to change

o Frequency can change if the source or the receiver move o High pitch to low pitch as it moves away from you

The Doppler Effect is NOT observed where the following occurs: both the  observer and the source are moving at the same velocity

∙ Transmission—wave passes through matter

∙ Absorption—wave and energy absorbed

∙ Scattering—waves absorbed and reemitted Don't forget about the age old question of How many half steps is a perfect 4th?

o Diffuse scattering

o Reflection

∙ Refraction—bending of the light wave

3/2/16

∙ Electromagnetic Spectrum

o Maxwell’s equations

 Predicted more waves

o Hertz

∙ Range: kilohertz to hundreds of megahertz

∙ Longest waves

 Microwaves

∙ Range: 1mm – 1m

∙ Range: 1mm – 1micrometer (μ)

∙ All warm objects emit radiation

 Visible light

∙ Range: 700nm – 400nm

∙ Colors

o Slices of electromagnetic spectrum

∙ Ex) Black & blue or white & gold dress

∙ Human color perception is dependent upon the

interaction of all receptor cells with light, and this

combination results in nearly trichromic stimulation

∙ Range: 400nm – 100 nm

∙ Shorter wavelength = more energy We also discuss several other topics like What are the applications of derivatives?

o Damage to cells

∙ Fluorescence

 X ray and Gamma rays

∙ X rays

o Range: 100nm – 0.1nm

o High-frequency

o Medicine

∙ Gamma rays

o 0.1nm (10-10m) – 10-12m

o highest frequency

o medicine

o astronomy

3/4/16

Ch.8 The Atom

∙ great idea: all of the matter around us is made of atoms, the chemical  building blocks of our world

∙ the smallest pieces

o Democritus (Greek, ca. 460 BC – ca. 370 BC)

o Cut matter to reach the smallest piece

 Called “the atom” or “uncuttable”

∙ Elements

o John Dalton (English, 1766-1844)

 Father of modern atomic theory

 Cannot break down elements

 Elements composed of atoms

∙ Ex) water molecule is 1 oxygen atom and 2 hydrogen

atoms

∙ Are atoms real?

o Evidence for the reality of atoms

 Behavior of a gas

∙ Ideal of gas equation

∙ Change the pressure/volume of gas, temp changes  accordingly

∙ All comes about from the motion of individual

particles

∙ Bernoulli (Dutch-Swiss, 1700-1782)

o Atoms have mass and velocity and thus kinetic

energy

o Decreasing volume increases pressure

o Increasing temp increases pressure

 Chemical combinations

∙ Dalton discovered the law of definite proportions o Elements combine in a specific ratio of

weights

 Ex) water is 8-parts oxygen to 1-part

hydrogen (in weights)

o Ratio of weights is a small whole number

 Ex) 12 lbs carbon can combine with

either 16 lbs or 32 lbs of oxygen, but not

with 24 lbs of oxygen

o Implication: some units of elements are

fundamentally indivisible

∙ Radioactive carbon to figure out the cycle for

chlorophyll (carbon dioxide to oxygen for plants)

∙ Discovered in 1896

∙ Phosphors flash when hit by radiation

∙ 1903 demonstration of the twinkling caused by this  effect

 Brownian motion

∙ Einstein

∙ Motion due to individual particles

∙ Without those, you wouldn’t see those movements in fluid

∙ Erratic, jiggling, motion

o Pollen grains suspended in water

 X-ray crystallography

∙ Freeze proteins, shoot X-rays at them to figure out  the structure of proteins

∙ Used for medical uses

 Atomic-scare microscopy

∙ Actually see individual molecules/atoms

∙ The structure of an atom

o Joseph Thomson

 Identified electron (1897)

∙ Negatively charged, smaller & lighter than the

smallest atom

 Said atoms are NOT fundamental building blocks, but are  made up of smaller more fundamental particles

 Basically, atoms are the smallest thing that make a thing a  thing

 If you get smaller than an atom, its still stuff (electrons) o The atomic nucleus

 Ernest Rutherford

∙ Determined atomic structure

o Atom has a nucleus at center surrounded by

electrons

∙ Later discoveries found nucleus is composed of

protons and neutrons

∙ Problems with Rutherford’s model of the atom

o Why?

 Object in circular orbit is accelerating

 Accelerated electrical charge emits

 Electrons giving off energy while

orbitings

∙ Result: electrons spin towards

nucleus and eventually atom

ceases to exist

o Rutherford atom exists <1 min.

∙ The nuclear regulatory commission

o Logo: highly stylized atomic model

 The Bohr Atom

o First working model of atom

o Energy levels for electrons

 Specific distances from nucleus

 Electrons exist with no radiation

 Electrons cannot exist between allowed distances (energy  levels)

o Energy in Bohr Atom

 Energy required to leave ground state

∙ Absorb proton

∙ Heat

o Increases collisions

 Photons: particles of light

o Photon absorbed

 Used to move electron to a higher energy state

o Photon emitted as electron moves to lower energy state o Quantum leap or jump – electron disappears from original  location and reappears in final location – NEVER at positions in  between

 Spectroscopy

o Atoms emit and absorb different photons

o Depends on differences between energy levels

o Each atom has distinct set of photons

o Spectrum

 All photons emitted by an atom

 Used for identification

o Glass prism

 The science of life

o Spectra of life’s chemical reactions

 Used to determine how enzymes work

 Used to identify pollutants emitted from automobile  exhaust pipes

 Technology

o Lasers

 Produce a beam of light

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