Electromagnetic Radiation and X-Rays

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Electromagnetic Radiation and X-Rays"It's of no use whatsoever[...] this is just an experiment that proves Maestro Maxwell was right - we just have these mysterious electromagnetic waves that we cannot see with the naked eye. But they are there." Heinrich Hertz

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Spectroscopy and X-Ray Analysis Electromagnetic Radiation

Electromagnetic waves Calculations involving waves The electromagnetic spectrum Light and Optics Refraction and diffraction

X-Rays Discovery of X-rays Generation of X-rays Quantum Numbers Electron Energy Transitions

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The Electromagnetic Waves

Light waves are self propagating waves that consist of both an electronic and magnetic component.

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Formulas for Waves

Propagation Speedc = λfc is speed of propagation, (m/s)λ is wavelength, (m)f is frequency (/s, Hz, s-1)

PeriodT = 1/ff = 1/TWhere:T is the period (s)f is the frequency (Hz)

EnergyE = hfWhere:E is the energy of the photonh is Planck’s constantf is the frequency of the radiation

For light c is constant and equal to 2.998 x 108 m/s

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The Electromagnetic Spectrum

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EM Radiation Activity You will each be assigned one of the following

types of electromagnetic radiation. Look it up. Report the following information for it: Wavelength How it is generated What it are some common uses

Gamma rays, X-rays, Ultraviolet radiation, Light, Infra-red radiation, Microwaves, Radio waves (FM, AM, ELF), Gravity waves.

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CalculationsCalculate the frequency of a red laser pointer light with wavelength 655 nm.

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CalculationsCalculate the wavelength and type of electromagnetic radiation you would expect to produce from a 3 GHz computer.

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CalculationsA common unit in spectroscopy is the “wave number” which is usually defined as the number of waves per cm.

How many wave cycles per cm (wave numbers) would you expect to find in radiation produced from a microwave oven operating at a frequency of 2450 MHz?

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CalculationsCopper emits a kα X-ray of 8.04 keV. What would the wavelength be?

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Light and Optics Electromagnetic radiation

What we see as light is part of the electromagnetic spectrum.

Photon: a unit of electromagnetic energy (light). Photons have no electric charge, they have zero “rest mass” but they do have momentum and energy.

http://hyperphysics.phy-astr.gsu.edu/hbase/emwav.html#c1

http://en.wikipedia.org/wiki/Electromagnetic_radiation

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Discovery of X-rays

Wilhelm Röntgen

1895

http://en.wikipedia.org/wiki/X-ray

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X-ray Tube

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Two methods for generating X-rays

Bremsstrahlung / Braking Ionization / Characteristic

http://www.antonine-education.co.uk/Physics_A2/Options/Module_6/Topic_7/topic_7_x.htm

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X-Ray Analysis Quantum numbers Electron Shells Allowed electron transitions

http://www4.nau.edu/microanalysis/Microprobe/Probe.html

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Quantum NumbersNumber Name Permitted Values Defines

n Principal (1, 2, 3, …) Electron shell

(1=K, 2=L, 3=M …)

l Azimuthal 0 to n-1 Electron cloud shape

ml Magnetic -l to +l Electron shell

orientation in a magnetic field

msSpin ±½ Electron spin

direction

j = l + ms Inner precession

l + ms

l ± ½

But j≠ -½

Total angular momentum

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Principle Quantum Number, n

Shell Designation

Subshells

l

Number of states

Number of electrons

per subshell

per shell

1 K s 1 2 2

2 L s 1 2 8

p 3 6

3 M s 1 2 18

p 3 6

d 5 10

4 N s 1 2 32

p 3 6

d 5 10

f 7 14

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Electron ShellsK LI LII LIII MI MII MIII MIV MV

n 1 2 2 2 3 3 3 3 3

l 0 0 1 1 0 1 1 2 2

s +½ +½ -½ +½ +½ -½ +½ -½ +½

j ½ ½ ½ 1½ ½ ½ 1½ 1½ 2½

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Electron ShellsK

1s

LI

2s

LII

2p

-½

LIII

2p

+½

MI

3s

MII

3p

-½

MIII

3p

+½

MIV

3d

-½

MV

3d

+½

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Electron Transitions1. The change in n must be ≥ 1 (Δn ≠ 0)

2. The change in l can only be ±1

3. The change in j can only be ±1 or 0

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Calculation 1. The change in n must be ≥ 1 (Δn ≠ 0)

2. The change in l can only be ±1

3. The change in j can only be ±1 or 0

Quantum #

Δ

n

l

ml

ms

j

2p +½ to 1s

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Example of Electron Transitions

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Spectroscopy and X-Ray Analysis Electromagnetic Radiation

Electromagnetic waves Calculations involving waves The electromagnetic spectrum Light and Optics Refraction and diffraction

X-Rays Discovery of X-rays Generation of X-rays Quantum Numbers Electron Energy Transitions