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"Is affirmed"
At methodical session of the chair of medical
and biological physics
2007. The report №
chief of chair
Shaplavskij M.V.
Methodical instructions (indication)
for plan students self- preparation
“EMW in medicine”
Module 3: Basic regularities of electromagnetism, atimic and nuclear physics.
Pithy module 6. Influence of physical factors on human body.
Chernivtsi-2007
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Objective:.
Introduction:
The different parts of the electromagnetic spectrum have very different effects
upon interaction with matter. Starting with low frequency radio waves, the human
body is quite transparent.
Background:
1..
Basic question:
1.
Practical exercise:
1.
Final knolege and skills:
Students should know:
Students should be able:
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Contents of theme
1. Classical Wave Description of Electromagnetic Waves in Vacuum
Maxwell’s Prediction of EM Waves
 The Derivation of Equations for Electromagnetic Waves from
Maxwell’s Equations
 Electromagnetic Waves Generated by a Sinusoidal Oscillator
2. Production of electromagnetic waves by an antenna
3. Properties of electromagnetic waves
4. The spectrum of electromagnetic waves
 Radio waves
 Infrared waves
 Visible light
 Ultraviolet (uv) light
 X-rays
 Gamma rays
5. Historical Background—Wave versus Particle Behavior of EM radiation
6. Relationships of photons and waves
 Postulates of quantum mechanics
7. Interaction of electromagnetic radiation with matter
1. Atomic interactions
 Microwave interactions (Rotational transitions)
 Infrared interactions (Vibrational transitions)
 Infrared interactions (Vibrational transitions)
 Electronic transitions
2. Visible Light Interactions
3. Ultraviolet Interactions
4. Macroscopic interactions
 Reflectance, absorption and transmittance
 Specular and diffuse reflection
8. Planck's Quantum Theory
9. The Photoelectric Effect
. Literature
1. Raymond A.Serway, Jerry S. Faughn Colloge physics, Fifth Edition.-Saunders
College Publishing.- 1999.-1029 p.
2. Marzeniuk V.P., Diduch V.D., Vakulenko D.V. et al. Biophysics and medical
informatics.- Ternopil: Ukrmedkniha, 2004.-480p.
3. Hugh D. Young, Roger A. Freedman University physics with modern physics,
11th edition.-Pearson education.-2004.-1714p.
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4.Frank J. Blatt Modern Physics .-McGRAW-HILL, INC.-1992.- 517 p.
5. Methodical instructions (indication) for student’s preparation, lecture.
Questions for self-preparation of students:
1. The Derivation of Equations for Electromagnetic Waves from Maxwell’s
Equations
2. Electromagnetic Waves Generated by a Sinusoidal Oscillator
3. Production of electromagnetic waves by an antenna
4. Properties of electromagnetic waves
5. The spectrum of electromagnetic waves
 Radio waves
 Infrared waves
 Visible light
 Ultraviolet (uv) light
 X-rays
 Gamma rays
6. Historical Background—Wave versus Particle Behavior of EM radiation
7. Relationships of photons and waves. Postulates of quantum mechanics
8. Atomic interactions
 Microwave interactions (Rotational transitions)
 Infrared interactions (Vibrational transitions)
 Infrared interactions (Vibrational transitions)
 Electronic transitions
9. Visible Light Interactions
10. Ultraviolet Interactions
11. Macroscopic interactions
 Reflectance, absorption and transmittance
 Specular and diffuse reflection
12. Planck's Quantum Theory
13. The Photoelectric Effect
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Tests.
1. Human body is source eloctromagnetic waves of
a)
Infrared region with λmax=9,6 m
b)
Red region with λmax=0,69 m
c)
Ultraviolet region with λmax=300 nm
d)
X-ray region with λmax=9 nm
2. Point out unit of magnetic induction B
a) H (henry)
b) T (tesla)
c) Wb (weber)
d) F (farad)
Class independent work
Interaction of electromagnetic radiation with matter
The different parts of the electromagnetic spectrum have very different effects upon
interaction with matter. Starting with low frequency radio waves, the human body is quite
transparent. (You can listen to your portable radio inside your home since the waves pass freely
through the walls of your house and even through the person beside you!) As you move upward
through microwaves and infrared to visible light, you absorb more and more strongly. In the
lower ultraviolet range, all the UV from the sun is absorbed in a thin outer layer of your skin. As
you move further up into the x-ray region of the spectrum, you become transparent again,
because most of the mechanisms for absorption are gone. You then absorb only a small fraction
of the radiation, but that absorption involves the more violent ionization events. Each portion of
the electromagnetic spectrum has quantum energies appropriate for the excitation of certain
types of physical processes. The energy levels for all physical processes at the atomic and
molecular levels are quantized, and if there are no available quantized energy levels with
spacings which match the quantum energy of the incident radiation, then the material will be
transparent to that radiation, and it will pass through.
Microwave interactions (Rotational transitions)
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The quantum energy of microwave photons is in the range 0.00001 to 0.001 eV which is in
the range of energies separating the quantum states of molecular rotation and torsion. The
interaction of microwaves with matter other than metallic conductors will be to rotate molecules
and produce heat as result of that molecular motion. Conductors will strongly absorb
microwaves and any lower frequencies because they will cause electric currents which will heat
the material. Most matter, including the human body, is largely transparent to microwaves. High
intensity microwaves, as in a microwave oven where they pass back and forth through the food
millions of times, will heat the material by producing molecular rotations and torsions.
Rotational transitions may also occur in the rotational properties of molecules, but they are
restricted to gases. They relate to changes in the momentum of inertia of the rotating molecules
of gas. Rotational transitions are of most importance, together with vibrational transitions, in the
interaction between EMR and the atmospheric gases through which the Earth’s surface must be
viewed by the remote sensing system.
Infrared interactions (Vibrational transitions)
Vibrational transitions result in changes in the relative disposition of the component atoms
of molecules. The quantum energy of infrared photons is in the range 0.001 to 1.7 eV which is in
the range of energies separating the quantum states of molecular vibrations. All these discrete
wavelengths superimposed together comprise a band within which transitions are induced.
Infrared is absorbed more strongly than microwaves, but less strongly than visible light. The
easiest to visualize are distorsions of bonds, either stretching or bending from one equilibrium
state to another. The result of infrared absorption is heating of the tissue since it increases
molecular vibrational activity. Infrared radiation does penetrate the skin further than visible light
and can thus be used for photographic imaging of subcutaneous blood vessels. Like electronic
transitions, those associated with molecular vibrations and bonds characterize solids, liquids and
gases.
Electronic transitions
Electronic transitions involve shifts of electrons from one quantum shell to another. A
photon of a specific wavelength may induce an electron to move from a lower orbit to a higher
one, thereby allowing the EMR energy to be absorbed. The wavelengths that can cause
electronic transitions are determined by the principal quantum numbers, angular momentum and
spin associated with quantum shells within a particular element. Such electronic transitions occur
in solids, liquids and gases, but are particularly important for elements like iron, which have
several possible valence states, positions in molecular structures and coordinations in natural
materials. Since electronic transitions require high excitation energies, they are most common at
short wavelength ultraviolet and visible light.
Ultraviolet Interactions
The near ultraviolet is absorbed very strongly in the surface layer of the skin by electron
transitions. As you go to higher energies, the ionization energies for many molecules are reached
and the more dangerous photoionization processes take place. Sunburn is primarily an effect of
UV, and ionization produces the risk of skin cancer.
The ozone layer in the upper atmosphere is important for human health because it absorbs
most of the harmful ultraviolet radiation from the sun before it reaches the surface. The higher
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frequencies in the ultraviolet are ionizing radiation and can produce harmful physiological
effects ranging from sunburn to skin cancer.
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