Light Waves

X-rays

3 x 108 m/sF = c / = 2.19 x 10-10 m

= 1.37 x 1018 Hz

Radio Waves

Live 105:105.3 MHz

3 x 108 m/s

= c / f = 105.3 x 106 Hz

= 2.85 m

Red Light

= 728 nm = 7.28 x 10-7 m

3 x 108 m/sf = c/ = 7.28 x 10-7 m

= 4.12 x 1014 Hz

Light Energy

Planck’s Law:E = h f

High frequency -> High energy

Properties of Light

Reflection:

Specular &diffuse

Refraction

“Bending” of light rays

With a change in media

Light rays and vision

Myopia (Nearsightedness)

Lens Correction

Hyperopia (Farsightedness)

Lens Correction

Refracting Telescope

Refraction

Index of Refraction

cn = v

Refraction due to Temperature

“mirages”

Refraction via (temperature)

n (air 0ºC) = 1.0029

n (air 30ºC) = 1.0026

Light travels faster in warm air

Refractive Index valuesMaterial Refractive Index

Air 1.0003

Water 1.33

Glycerin 1.47

Oil 1.515

Glass 1.52

Zircon 1.92

Diamond 2.42

Laser

Single frequency

Focused

Single direction

Incandescent Light Bulb

Filament heated to glow

All visible light frequencies

All directions

Wave Vs. Particle?

Young’s experiment

Photoelectric Effect

Quanta

E = h x f

High frequency photonshave more energy

Electron Ejection

Bohr model for Hydrogen

Niels Bohr

What about more complex atoms?

Atomic Theory

Leucippus & Democritus4th century BC

“indivisible”eternal, moving

Elements

Aristotle

Continuous matter

Natural motion

Age of Experimentation

Lavoisier (1743 - 1794)

Conservationof matter

Lavoisier

“Traite Elementaire de Chimie”

HgO --> Hg + oxygène

Dalton

Elements made of atoms

All atoms of one element are the same but different than those of other elements

Atoms of different elements can form different combinationswith different properties

Compounds

Water Hydrogen Peroxide

H2O H2O2

Compounds

Nitrous oxide Nitrogen DioxideN2O NO2

Dalton

Atomic masses

Benjamin Franklin

Like charges - Repel

Unlike charges - Attract

Michael Faraday

Ions = Charged atoms

+/- Charged Particles

J.J. Thomson (1897) Cathode rays

The Size of an Electron

Millikan (1911)

me = 9.11 x 10-31 kg 1 H atom

= 1840

Positive Particle?

Rutherford (1907)

particle = He+ nucleus

Neutrons

Chadwick (1932)

Neutron = neutral = “spacer”

Atomic Structure

Plum pudding planetary

Subatomic particles

Quarks

Atomic Number

Atomic Number = # of protons

Atomic Mass = protons + neutrons

Isotopes

€

1

1H 1

2H 1

3H

Unstable Isotopes

Radioactivity

Henri Becquerel

Radioactivity

Marie Sklodowskaand Pierre Curie

Alpha Decay

€

92

238U - - - -- > 2

4He + 90

234Th

Beta Decay

€

88

228Ra - - - -- > 89

228Ac + -1

0e

Gamma Radiation

Radiation Safety

Paper

Al foil

Lead

Artificial Elements

€

92

238U + 6

12C - - - -- > 98

244Cf + 60

1n

€

98

249Cf + 8

15O - - - -- > 106

263Sg + 4 0

1n

Rate of Decay: Half Life

Isotope Half Lives

Isotope Half Life

U - 238 4.5 x 109 years

Pu - 239 24,360 years

C - 14 5730 years

Co - 60 5.3 years

I - 131 8 days

Po - 214 1.63 x 10-4 sec

Medical Radioisotopes

99Tc and 123I

Technetium Half life

99Tc half life = 6 hours

If 10 g injected into a patient, how much is left after 24 hrs?

24 hrs = 4 x 6 hrs = 4 half lives

10 g -> 5 g -> 2.5 g -> 1.25 g -> 0.625g

Radiocarbon Dating

Atomic Clock

Radiocarbon Dating

Shroud of Turin

Ice Man (Ötzi)

Nuclear Fission

Otto Hahn &Lise Meitner

€

0

1n + 92

235U - - - - > 56

141Ba + 36

92Kr + 3 0

1n

Chain Reaction

Fission Energy

Control rods= moderators

usually Boron, Carbon

Keep reactionunder control

Manhattan Project

US Fission Reactors

Three Mile Island (TMI) 1979

Chernobyl 1986

Breeder Reactor

Fast Breeder Reactions

Radioactive Waste

Fusion

Fusion into Heavier Elements

Fission vs. Fusion

High energy higher energy

Radioactive waste no radioactivity

Need fissionable small commonnuclei atoms

Currently used need solar conditions

Cold Fusion (1989)

Fleischman/Pons (Utah)

Cold Fusion

Cold Fusion (2005)

Naranjo, Gimzewski & Putterman

Using a strong Electric Field

Tokamak reactor

Chemical Reactions

Proton Transfer Electron Transfer

H+ e-

acids/bases reduction/oxidation

Proton Transfer

Acid: Sour taste, corrosive Releases H+

Base (alkaline): bitter, corrosiveAccepts H+

Identifying Acids, Bases

2 HBr + CaO --> H2O + CaBr2

Identifying Acids, Bases

2 HBr + CaO --> H2O + CaBr2

ACID BASE

All proton transfer reactions must haveBOTH an acid and a base

Amphoteric Compounds

H2O + HCl --> H3O+ + Cl–

H2O + NH3 --> OH– + NH4+

pH

“pouvoir hydrogène”

pH = – log10 [H+]

Acid: excess H+, low pH

Base: H+ deficit, high pH

pH scale

Low pHacid

pH = 7neutral

High pH basic

“pH Balanced”

Buffers

Combination of acid/base form designed to keep pH at setlevel

Antacids

Excess Stomach Acid

Overindulgence

Skipping meals

Stress

Antacid = Mild Base

Sodium BicarbonateNaHCO3

NaHCO3 + HCl --->

H2CO3 ---> carbonic acid

CO2 + H2O

Sodium - Free?

Hypertension

Alka SeltzerNaHCO3 + aspirin + citric acid

Calcium Carbonate

Twice the acid relief!

CaCO3 + 2 HCl --->

H2CO3 --->

CO2 + H2O

Milk of Magnesia

No gas

Mg(OH) 2 + 2 HCl ->

2 H2O + MgCl2

High dose = laxative

Acid Rain

Rainfall with ph < 5.5

Normal rainis mildly acidic

due to H2CO3 (carbonic acid)

Locations

Causes

Impurities in fossil fuels: N, S (+ O2)

NOx, SOx

Effects of Acid Rain

Limestone, marble erosion

Effects of Acid Rain

Chemical Reactions

Proton Transfer Electron Transfer

H+ e-

acids/bases reduction/oxidation

Electron Transfer

Oxidation electron loss

Reductionelectron gain

Electron Transfer

Oxidation electron loss

2 Ag --> 2 Ag+ + 2 e-

Reductionelectron gain

silver tarnishingS + 2 e- --> S2-

Electron Transfer

OxidationOxygen gain C + O2 --> CO2

Hydrogen loss NH4+ --> N2 (rocket fuel)

Reduction

Oxygen loss ClO4- --> Cl2 (rocket fuel)

Hydrogen gain C18H34O2 --> C18H36O2unsat Oleic acid sat Stearic acid

Safety Matches

3 S + 2 KClO3 -> 2 KCl + 3 SO2

ox

Red

Biological Redox

Alcohol metabolism

Alcohol Metabolism

Acetic acid

Liveralcoholdehydrogenase

Aldehydeoxidase

Hangover

Nausea

Headache

Sensitivity tolight, sound

Batteries

Daniell cell: Cu and Zn

Battery Operation

Anode: oxidation Zn -> Zn2+ + e-

Cathode: where reduction occurs

MnO2 + e- Mn2O3

Alkaline Batteries

Anode: Manganese

Cathode: Zinc

Rechargeable Batteries

Ni-cad

Cd -> Cd2+ + e-

NiO2 + e- -> NiO

NiMH batteries

Higher capacity

Longer lifetime

NiOOH -> Ni(OH)2 (Ni+/Ni2+ oxidation)M+H- -> M (reduction)

Lead-Acid Batteries

Pb + SO42- -> PbSO4 + 2e-

PbO2 + 4 H+ + SO42- + 2e- -> PbSO4 + H2O

Corrosion

Fe -> Fe2+ oxidation

O2 -> OH- reduction

Statue of Liberty

Gift fromFrance 1876

Renovation (1986)

Capturing Light

Louis Daguerre

Exposure

Silver salts: AgBr or AgI

Light + 2 Ag+ X- 2 Ag+* + X2

Development

Ag+* + C6H6O2 Ag + HBr + C6H4O2

Use Acid to Stop this process

Fixing

Removes excess insoluble Silver:

Ag+ + S2O32- Ag(S2O3)-

HYPO

Color Photography

Light + Ag+ + Dye -> Ag+* + Dye*

Instant Photography

Polaroids