Are you getting the concept? If the average irradiance from the Sun impinging normally on a surface just outside the Earth’s atmosphere is 1400 W/m 2,

Slides:



Advertisements
Similar presentations
Fluorescent Lamps.
Advertisements

Spectrochemical Instrumentation Modules
The learning objectives for this course are: (1) Critically consume scientific literature and talks in the area of analytical spectroscopy. Pose meaningful.
Discharge Lamps Chapter 14 part2 1020C.
UV instrumentation Abu Yousuf, PhD Associate Professor Department of Chemical Engineering & Polymer Science Shahjalal University of Science & Technology.
METO 621 Lesson 6. Absorption by gaseous species Particles in the atmosphere are absorbers of radiation. Absorption is inherently a quantum process. A.
PHYSICS 103: Lecture 20 Blackbody Radiation Light Bulbs Agenda for Today:
Atomic Absorption Spectroscopy Prof Dr Hisham E Abdellatef 2011.
AA and Atomic Fluorescence Spectroscopy Chapter 9
Light. Photons The photon is the gauge boson of the electromagnetic force. –Massless –Stable –Interacts with charged particles. Photon velocity depends.
What are the 3 ways heat can be transferred? Radiation: transfer by electromagnetic waves. Conduction: transfer by molecular collisions. Convection: transfer.
EM Radiation Sources 1. Fundamentals of EM Radiation 2. Light Sources
Lesson 7: Remote Sensing Dr Andrew Ketsdever MAE 5595.
Introduction to Quantum Physics
Describing a Real Source 1) Identify m of real source and adjust T in to line up m 2) The ratio of: 3) Measure T w ( ) to calculate  ( ) Ingle and Crouch,
Black Body radiation Hot filament glows.
EM Radiation Sources 1. Fundamentals of EM Radiation 2. Light Sources 3. Lasers.
Geometric Optics consider only speed and direction of a ray
Overall Ingle and Crouch, Spectrochemical Analysis.
Describing a Real Source 1) Identify m of real source and adjust T in to line up m 2) The ratio of: 3) Measure T w ( ) to calculate  ( ) Ingle and Crouch,
Transducers Converts one type of energy into another. Light  Electrical (current, voltage, etc.) What characteristics should we look for in a transducer?
The birth of quantum mechanics Until nearly the close of the 19 th century, classical mechanics and classical electrodynamics had been largely successful.
Electromagnetic Spectrum The energy of the photon determines the type of transition or interaction that occurs. Table 1-1 – Ingle and Crouch, Spectrochemical.
Physics 361 Principles of Modern Physics Lecture 3.
Reminder of radiance quantities I λ RadianceW m -2 μm -1 sr -1 Intensity (Monochromatic) F λ Spectral IrradianceW m -2 μm -1 Monochromatic Flux F(Broadband)
Images:
Ch. 5 - Basic Definitions Specific intensity/mean intensity Flux
Laws of Radiation Heat Transfer P M V Subbarao Associate Professor Mechanical Engineering Department IIT Delhi Macro Description of highly complex Wave.
 Radiation emitted by hot objects is called thermal radiation.  Recall that the total radiation power emitted is proportional to T 4, where T is the.
Chapter 18 Bose-Einstein Gases Blackbody Radiation 1.The energy loss of a hot body is attributable to the emission of electromagnetic waves from.
Blackbody radiation How does a solid contain thermal energy? Can a vacuum be “hot”, have a temperature? Why does solid glow when it’s hot? Yes its fields.
1 P1X: Optics, Waves and Lasers Lectures, Lasers and their Applications i) to understand what is meant by coherent and incoherent light sources;
Lighting System A lighting system consists of : 1.Light sources 2.Luminaires (or fixtures) 3.Ballasts.
Average Lifetime Atoms stay in an excited level only for a short time (about 10-8 [sec]), and then they return to a lower energy level by spontaneous emission.
1 Introduction to Spectroscopic methods Spectroscopy: Study of interaction between radiation (or other forms of energy) and matter (a branch of science).
Unit 6: Electrons in Atoms part 1: properties of waves.
Energy Levels & Photons Atomic & Nuclear Lesson 2.
How to Make Starlight (part 1) Chapter 7. Origin of light Light (electromagnetic radiation) is just a changing electric and magnetic field. Changing electric.
Photon Statistics Blackbody Radiation 1.The energy loss of a hot body is attributable to the emission of electromagnetic waves from the body. 2.The.
Physics 1C Lecture 28A. Blackbody Radiation Any object emits EM radiation (thermal radiation). A blackbody is any body that is a perfect absorber or emitter.
Radiation Fundamental Concepts EGR 4345 Heat Transfer.
Radiation Heat Transfer EGR 4345 Heat Transfer. Blackbody Radiation Blackbody – a perfect emitter & absorber of radiation Emits radiation uniformly in.
Substitute Lecturer: Jason Readle Thurs, Sept 17th, 2009
CBE 150A – Transport Spring Semester 2014 Radiation.
Blackbody Spectrum Remember that EMR is characterized by wavelength (frequency) Spectrum: distribution of wavelength (or frequency) of some EMR Blackbody:
Introduction to Thermal Radiation and Radiation Heat Transfer.
Physics 1202: Lecture 30 Today’s Agenda Announcements: Extra creditsExtra credits –Final-like problems –Team in class HW 9 next FridayHW 9 next Friday.
Major lamp types. LAMP CHARACTERISTICS 1. Light production mechanisms 2. Principle lamp characteristics 3. Characteristics of three main lamp types (I)
Radiation (Ch 12 YAC) Thermal energy is emitted by matter as a result of vibrational and rotational motion of molecules, atoms and electrons. The energy.
Recall that light is EM radiation and is therefore characterized by its wavelength. Recall that light is EM radiation and is therefore characterized by.
Dualisme Cahaya Sebagai Gelombang dan Partikel
Light is a Particle Physics 12.
This Week (3) Concepts: Light and Earth’s Energy Balance Electromagnetic Radiation Blackbody Radiation and Temperature Earth’s Energy Balance w/out atmosphere.
Reminder of radiance quantities I λ RadianceW m -2 μm -1 sr -1 Intensity (Monochromatic) F λ Spectral IrradianceW m -2 μm -1 Monochromatic Flux F(Broadband)
Blackbody. Kirchhoff’s Radiation  Radiated electromagnetic energy is the source of radiated thermal energy. Depends on wavelengthDepends on wavelength.
Life always offers you a second chance. It’s called tomorrow.
Wavelength, Frequency, and Planck’s Constant. Formulas 1)E = hf E = energy (Joules J) h = Planck’s constant = 6.63 x J x s f = frequency (Hz) 2)
Light and The Electromagnetic Spectrum Why do we have to study “light”?... Because almost everything in astronomy is known because of light (or some.
Physical Principles of Remote Sensing: Electromagnetic Radiation
Plan for Today (AP Physics 2) Questions on HW (due tomorrow) Notes/Lecture on Blackbody Radiation.
Basic Science in Remote Sensing
Quantum Mechanics I Quiz Richard Feynman, bongo drummer and physicist
Lecture 20 Light and Quantized Energy Ozgur Unal
Topic- Black-Body Radation Laws
Black Body Radiation Mr. Sonaji V. Gayakwad Asst. professor
Radiation in the Atmosphere
SPECTROPHOTOMETRY Applied Chemistry.
Introduction and Basic Concepts
Light and The Electromagnetic Spectrum
RADIATION LAWS.
Presentation transcript:

Are you getting the concept? If the average irradiance from the Sun impinging normally on a surface just outside the Earth’s atmosphere is 1400 W/m 2, what is the resulting pressure (assuming complete absorption)? How does this pressure compare with atmospheric pressure (~ 10 5 N/m 2 )? T = I/c T = I/c = (1400 W/m 2 )/(3.00 x 10 8 m/s) = 4.7 x W/m·s = (1400 W/m 2 )/(3.00 x 10 8 m/s) = 4.7 x W/m·s = 4.7 x N/m 2 = 4.7 x N/m 2 This pressure is less than 5 x % of atmospheric pressure. When accounting for the surface area of the Earth (5.11 x m 2 ), this provides 2.4 x 10 5 tons of force. Reminder: 1 W = 1 J/s = 1 N·m/s = 1 kg·m 2 /s 3

Photon Emission E. Hecht, Optics, atom in ground stateatom in ground state atom excited by high T or collision, stays in excited quantum state for or secatom excited by high T or collision, stays in excited quantum state for or sec atom returns to ground state, emitting a photonatom returns to ground state, emitting a photon Frequency of emitted light is associated with the quantized atomic transition (  E = h )

Photon Radiation Figure 5-16 Partial energy-level diagram for a fluorescent organic molecule. Skoog and Leary, Principles of Instrumental Analysis, 1992.

Are you getting the concept? Many streetlights are sodium discharge lamps. The emitted orange light is due to the sodium D-line transition: What is the energy level spacing (in eV) for the 3p → 3s transition?

EM Radiation Sources 1. Fundamentals of EM Radiation 2. Light Sources 3. Lasers

Optical Source Characteristics Ingle and Crouch, Spectrochemical Analysis Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.

Continuum Source Line Source Continuum + Line Source Ingle and Crouch, Spectrochemical Analysis

Incandescent Lamp 1. Glass bulb (or "envelope") 2. Low pressure inert gas 3. Tungsten filament 4. Contact wire (goes to foot) 5. Contact wire (goes to base) 6. Support wires 7. Glass mount/support 8. Base contact wire 9. Screw threads 10. Insulation 11. Electrical foot contact

Black-body Radiation In an ideal Black body:  ( ) = 1,  ( ) = 0, T( ) = 0 Because a black body is at thermal equilibrium, emission must equal absorption. Thus, black bodies are perfect absorbers and the most efficient emitters possible. There are no ideal black bodies.

Spectral Distribution of Emission is Characteristic of the Temperature of the Blackbody As T increases, max decreases. Donald McQuarrie, Quantum Chemistry, University Science Books, Mill Valley, CA,

Rayleigh – Jeans Law  Spectral Radiance (Jm -3 s -1 ) (Jm -3 s -1 ) The Ultraviolet Catastrophe Approximate Blackbody Expressions Wien’s Law

Resolved (inadvertently) in 1900 by Max Planck. Assumed atoms could only absorb or emit discrete amounts of energy. Planck’s Radiation Law: Donald McQuarrie, Quantum Chemistry, University Science Books, Mill Valley, CA,  Spectral Energy Density (Jcm -3 Hz -1 ) (Jcm -3 Hz -1 )

Wien’s Displacement Law Eugene Hecht, Optics, Differentiate Planck’s Law with respect to and set equal to zero to find m (wavelength of maximum irradiance): Stefan-Boltzman Law M b =  T 4  =  W·cm -2 · K -4 Integrate Planck’s Law to find the total emittance of a black body:

Are you getting the concept? Suppose that we measure the emitted exitance from a small hole in a furnace to be 22.8 W/cm 2. Compute the internal temperature of the furnace.

Non-Ideal Sources – “Gray Bodies” Spectral radiance Spectral radiance of a true black body

Spectral Emissivity,  : Ratio of the spectral radiance of a true source to that of a black body Accounts for  < 1 Eugene Hecht, Optics, Addison-Wesley, Reading, MA,  =  ( ) Corrections for Non-Ideal Sources

T w ( ) is the transmission factor of the source envelope Corrections for Non-Ideal Sources

Color Temperature (T) T in is an adjustable parameter T is the temperature that the atoms experience

Are you getting the concept? Calculate the spectral radiance of a tungsten lamp at 500 nm with a color temperature of 2700 K,  = 0.40, and T  = 0.92 in J/m 3 s. Recall: k = 1.38 x J · K -1

Describing a Real Source 1) Adjust T in to line up max 2) The ratio of: 3) Measure T w ( ) to calculate  ( ) Ingle and Crouch, Spectrochemical Analysis

Nernst Glower Rare earth oxides formed into a cylinder (1-2 mm diameter, ~20mm long) Pass current to give: T = 1200 – 2200 K Can operate in air (no need for glass/quartz enclosure) Ingle and Crouch, Spectrochemical Analysis Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, 1992.

Globar Silicon Carbide Rod (5mm diameter, 50 mm long) Heated electrically to 1300 – 1500 K Positive temperature coefficient of resistance Electrical contact must be water cooled to prevent arcing Ingle and Crouch, Spectrochemical Analysis

Tungsten Filament Ingle and Crouch, Spectrochemical Analysis Heated to 2870 K in vacuum or inert gas Useful Range: 350 – 2500nm

Tungsten / Halogen Lamp I 2 or Br 2 added Reacts with gaseous W near the quartz wall to form WI 2 W is redeposited on the filament Gives longer lifetimes Allows higher temperatures (~3500 K) and thus higher apparent brightness

Arc Lamps Ingle and Crouch, Spectrochemical Analysis Electrical discharge is sustained through a gas or metal vapor Continuous emission due to rotational/vibrational energy levels and pressure broadening

H 2 or D 2 Arc Lamps Ingle and Crouch, Spectrochemical Analysis D 2 + E e-  D 2 *  D’ + D” + h D 2 + E e-  D 2 *  D’ + D” + h Energetics: E e- = E D 2 * = E D’ + E D” + h E e- = E D 2 * = E D’ + E D” + h Useful Range: 185 – 400 nm

Hg Arc Lamp Continuum + line source High power source Often used in photoluminescence Ingle and Crouch, Spectrochemical Analysis

Douglas A. Skoog and James J. Leary, Principles of Instrumental Analysis, Saunders College Publishing, Fort Worth, Hollow Cathode Discharge Tube Apply ~300 V across electrodes Ar + or Ne + travel toward the cathode If potential is high enough cations will sputter metal off the electrode Metal emits photons at characteristic atomic lines as the metal returns to the ground state

Hollow Cathode Discharge Tube Line widths are typically 0.01 – 0.02 Å FWHM Ingle and Crouch, Spectrochemical Analysis

Light-Emitting Diodes Operate with mW of power - ~80% efficiency Long lifetimes, stable output

Are you getting the concept? List one light source with each of the following characteristics. Common IR source: Spans UV – IR: Standard household/office lighting: Lights quickly to full brightness: Common atomic absorbance source: Common photoluminescence source: