Download Objectives What are X-rays? Electromagnetic Radiation

Objectives
PAM1014
Introduction to Radiation
Physics
• Electromagnetic Radiation
• Electromagnetic Waves
• Properties of Electromagnetic Radiation
• Electromagnetic Spectrum
• Inverse Square Law
“Electromagnetic Radiation”
Radiation”
What are X-rays?
Electromagnetic Radiation
• Electromagnetic Radiation
Radio & TV
Microwave
IR
• A singlesingle-frequency
EM wave exhibits a
sinusoidal variation
of electric and
magnetic fields in
space
X-rays
Visible UV
γ-rays
10 1 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13
Wavelength in metres
• Magnetic variation is
• Useful Characteristics
–
–
–
–
perpendicular to
electric field
Penetrate Matter
Interact with Matter
Cause Certain Materials to Fluoresce
Cause Certain Material to Produce Electric Charge
Electromagnetic Waves
Sinusoidal Model
• Amplitude, A
Magnetic
Field
Electromagnetic Radiation
1 Cycle or Period (T)
• Transport energy through space
A
– Electric field
• Energy is stored in the propagating
• Wavelength
– Length of one cycle
λ
Electric
Field
Wavelength (λ)
electric and magnetic fields
• Frequency
– Hz = cycles per second
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Photons
Electromagnetic Spectrum
• A photon is the smallest quantity of
ANY type of electromagnetic radiation
• Energy disturbances moving through
• Frequency Range: 10 – 1024 Hz
• Wavelength Range: 106 – 10-16 m
• Regions relevant to medical imaging?
space at the speed of light
• c = 3 X 108 ms-1
Electromagnetic Radiation
Electromagnetic Spectrum
Energy
(eV)
eV)
Frequency
(Hz)
Wavelength
(m)
1010
1024
10-16
108
1022
10-14
X-ray
Imaging
106
1020
10-12
104
1018
Visual
Imaging
102
1016
10
1014
10-8
1μm 10-6
10-2
1012
10-4
10-4
1010
10-6
108
MR
Imaging
1nm
10-10
• Electromagnetic Radiation can interact
Gamma rays
X-rays
UV
Visible Light
IR
1cm 10-2
μ-wave
Radio
10-8
106
10-10
104
0
1m 10
102
1km
104
10-12
102
106
Gamma-Ray
• GammaGamma-Ray Imaging
with matter
• Interacts with particles matter of
length scale of the same order as the
radiation wavelength
X-ray
Astronomy
Security
Medical
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Ultraviolet
Astronomy
Optical
Microscopy
Band
Name
λ (μm)
uses
1
Vis blue
0.450.45-0.52
Max water penetration
2
Vis green
0.520.52-0.60
Measuring planet vigour
3
Vis red
0.630.63-0.69
Vegetation
4
NIR
0.760.76-0.90
Biomas & shoreline mapping
5
Middle IR
1.551.55-1.75
Moisture content
6
Thermal IR
10.410.4-12.5
Soil moisture & thermal mapping
7
Middle IR
2.082.08-2.35
Mineral mapping
NASA’
NASA’s LANDSAT satellite
Fluorescence Microscopy: Endothelial Cells, Astrocyte
Infrared
Optical
True color image; the red satellite
data (band3) is displayed in red, the
green satellite data (band 2) is
displayed in green, and the blue
satellite data (band 1) is displayed in
blue
Microwave
Astronomy
False color image;
image; any of the bands
can be put in a single color. The band
combination which is used can be
changed to highlight the desired
feature or phenomena.
Spaceborne Radar
Medical - MRI
Radio Imaging
Weather Radar
Astronomy – Radiotelescope
Gamma
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X-ray
Optical
IR
Radio
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Electromagnetic Waves
Electromagnetic Waves
Sinusoidal Model
• Frequency is
1 Cycle or Period (T)
• Amplitude
• Wavelength
– Length of one cycle
Wavelength (λ)
• Frequency
– Hz = cycles per second
Energy of Electromagnetic
Radiation
• Energy is proportional to frequency
• Energy = constant x frequency
OR
E = hf
the number of
wavelength
passing a point
per second
dis tan ce
time
velocity = frequency × wavelength
velocity =
= [ s −1 ][m] = [ms −1 ]
A
A
– Electric field
1 Cycle or Period (T)
Wavelength (λ)
c = fλ
Measurement of EM Radiation
Frequency, Wavelength & Energy
• Different regions of the electromagnetic
spectrum are measured in different ways
• Where h is Plank’
Plank’s constant
• h = 6.626 x 10-34 Js
Measurement of EM Radiation
• Visible light:
Example
• Calculate the energy of a 400 nm photon
• Early experiments describe light as a wave
– Quoted in meters
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Measurement of EM Radiation
• Radio waves:
Example
• Calculate the wavelength of 97.7 MHz
• Measured via oscillations of electrons in
conductors
– Quoted in Hz
Measurement of EM Radiation
• X-rays:
• Produced using electric potential
Example
• Calculate the frequency of a 50 keV xray photon
– Quoted in keV
• eV = the energy of one electron accelerate by
one volt
• E = hf
Ionizing Radiation
• Radiation with sufficient energy to
cause ionization
• Binding energy of outermost electron to
atoms ~10~10-100 ev
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Summary
• Electromagnetic Radiation
• Electromagnetic Waves
• Properties of Electromagnetic Radiation
• Electromagnetic Spectrum
• Inverse Square Law
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