This document provides an overview of electromagnetic radiation and its role in remote sensing. It defines key characteristics of electromagnetic waves like amplitude, wavelength, frequency, and speed. It describes the electromagnetic spectrum and different radiation types. Laws governing radiation like Kirchhoff's law, Stefan-Boltzmann law, and Wien's displacement law are covered. The document also discusses how radiation interacts with the atmosphere through scattering, absorption, and refraction.

1. Role of electromagnetic Radiation in
Remote Sensing
Student Name:
Class: Fourth Stage
Course Title: Remote Sensing
Department: Geomatics ( Surveying )
College of Engineering
Salahaddin University-Erbil
Academic Year 2019-2020
Copyright

2. 1
ABSTRACT
It should be clear by now that the electromagnetic waves are originator and
carrier of information in Earth observation. The information content of the
products delivered by a given type of sensor is essentially related to the
parameters, mainly frequency (or wavelength) and polarization,
characterizing the observing system, including the geometry at which data
are acquired. Therefore, the specifications of an EO system, which include
the type of sensor, the band of operation, the observation angle, etc.,
depend on the kind of information the system has to provide, as well as on
the required reliability of operation and quality of products.
Correspondingly, the interpretation of the data, preliminary to the retrieval
and corresponding put into use of information, must refer to the interaction
features of the electromagnetic wave with the observed environment. But,
since the waves originating and carrying the information must cross at least
once all or part of the atmosphere interposed between the target and the
sensor, accounting for the atmospheric interaction is also crucial both in
system specification and in data interpretation.

3. 2
TABLE OF CONTENTS
Abstract 1
Table of Contents 2
Introduction 3
Waves and their characteristics 4
Electromagnetic spectrum 7
Radiation types 8
Radiation laws 10
Conclusion 13
Reference 14

4. 3
Introduction
Electromagnetic radiation is a form of energy that is produced by
oscillating electric and magnetic disturbance, or by the movement of
electrically charged particles traveling through a vacuum or matter. The
electric and magnetic fields come at right angles to each other and
combined wave moves perpendicular to both magnetic and electric
oscillating fields thus the disturbance. Electron radiation is released as
photons, which are bundles of light energy that travel at the speed of light
as quantized harmonic waves. This energy is then grouped into categories
based on its wavelength into the electromagnetic spectrum. These electric
and magnetic waves travel perpendicular to each other and have certain
characteristics, including amplitude, wavelength, and frequency.
1. Electromagnetic radiation can travel through empty space. Most other
types of waves must travel through some sort of substance. For example,
sound waves need either a gas, solid, or liquid to pass through in order to
be heard.
2. The speed of light is always a constant. (Speed of light : 2.99792458 x
108 m s-1)
3. Wavelengths are measured between the distances of either crests or
troughs. It is usually characterized by the Greek symbol .

5. 4
Waves and their Characteristics
Fig. 1 & 2 : Electromagnetic Waves
Fig. 3 : An EM Wave

6. 5
Amplitude
Amplitude is the distance from the maximum vertical displacement of the
wave to the middle of the wave. This measures the magnitude of oscillation
of a particular wave. In short, the amplitude is basically the height of the
wave. Larger amplitude means higher energy and lower amplitude means
lower energy. Amplitude is important because it tells you the intensity or
brightness of a wave in comparison with other waves.
Wave length
Wavelength (λ) is the distance of one full cycle of the oscillation. Longer
wavelength waves such as radio waves carry low energy; this is why we
can listen to the radio without any harmful consequences. Shorter
wavelength waves such as x-rays carry higher energy that can be hazardous
to our health. Consequently lead aprons are worn to protect our bodies from
harmful radiation when we undergo x-rays. This wavelength frequently
relationship is characterized by:
c = λν (1)
where
 c is the speed of light,
 λ is wavelength, and
 ν is frequency.
Shorter wavelength means greater frequency, and greater frequency means
higher energy. Wavelengths are important in that they tell one what type of
wave one is dealing with.

7. 6
Fig. 4: Different Wavelengths and Frequencies
Frequency
Frequency is defined as the number of cycles per second, and is expressed
as sec-1
or Hertz (Hz). Frequency is directly proportional to energy and can
be express as:
E = hν (2)
where
 E is energy,
 h is Planck's constant, (h= 6.62607 x 10-34
J), and
 ν is frequency.
Period
Period (T) is the amount of time a wave takes to travel one wavelength; it is
measured in seconds (s).
velocity
The velocity of wave in general is expressed as:
velocity = λν
For Electromagnetic wave, the velocity in vacuum is 2.99×108
m/s or
186, 282 miles/second.

8. 7
Electromagnetic spectrum
Figure 24.5.1: Electromagnetic spectrum with light highlighted. from Wikipedia.
As a wave’s wavelength increases, the frequency decreases, and as wave’s
wavelength decreases, the frequency increases. When electromagnetic
energy is released as the energy level increases, the wavelength decreases
and frequency decreases. Thus, electromagnetic radiation is then grouped
into categories based on its wavelength or frequency into the
electromagnetic spectrum. The different types of electromagnetic radiation
shown in the electromagnetic spectrum consists of radio waves,
microwaves, infrared waves, visible light, ultraviolet radiation, X-rays, and
gamma rays. The part of the electromagnetic spectrum that we are able to
see is the visible light spectrum.
radiation, X-rays, and gamma rays. The part of the electromagnetic
spectrum that we are able to see is the visible light spectrum.

9. 8
Radiation types
Radio Waves are approximately 103
m in wavelength. As the name
implies, radio waves are transmitted by radio broadcasts, TV broadcasts,
and even cell phones. Radio waves have the lowest energy levels. Radio
waves are used in remote sensing, where hydrogen gas in space releases
radio energy with a low frequency and is collected as radio waves. They
are also used in radar systems, where they release radio energy and collect
the bounced energy back. Especially useful in weather, radar systems are
used to can illustrate maps of the surface of the Earth and predict weather
patterns since radio energy easily breaks through the atmosphere.
Microwaves can be used to broadcast information through space, as well
as warm food. They are also used in remote sensing in which microwaves
are released and bounced back to collect information on their reflections.
Microwaves can be measured in centimeters. They are good for
transmitting information because the energy can go through substances
such as clouds and light rain. Short microwaves are sometimes used in
Doppler radars to predict weather forecasts.
Infrared radiation can be released as heat or thermal energy. It can also
be bounced back, which is called near infrared because of its similarities
with visible light energy. Infrared Radiation is most commonly used in
remote sensing as infrared sensors collect thermal energy, providing us
with weather conditions.
This picture represents
a snap shot in mid-infrared light.

10. 9
Visible Light is the only part of the electromagnetic spectrum that humans
can see with an unaided eye. This part of the spectrum includes a range of
different colors that all represent a particular wavelength. Rainbows are
formed in this way; light passes through matter in which it is absorbed or
reflected based on its wavelength. Thus, some colors are reflected more
than other, leading to the creation of a rainbow.
Color Region Wavelength (nm)
Violet 380-435
Blue 435-500
Cyan 500-520
Green 520-565
Yellow 565-590
Orange 590-625
Red 625-740
Fig. 7: The color regions of the Visible Spectrum

11. 10
Radiation Laws
Kirchhoff's Law states that for all blackbodies at the same temperature, the
ratio of emitted radiation to absorbed radiation is the same. Emissivity is
then calculated as the ratio of the emittatnce of an object and the emittance
of a blackbody at the same temperature.
Stefan-Boltzmann Law states that the energy per unit area that a blackbody
emits increases as the temperature of the blackbody increases. Total
emitted radiation is calculated by:
Lastly, Wien's Displacement Law describes the relationship between the
wavelength of emitted radiation and the temperature of the object. This law
shows that as the temperature of an object increases the wavelength of
maximum emittance increaeses.
Interactions with the Earth's Atmosphere
All electromagnetic radiation must travel through the Earth's atmosphere
and along the way several things can happen to the radiation that alter the
radiation in some way either by redirection or a change in energy level.
The further away a sensor is from it's target, the the larger the atmospheric
effects are upon the radiation.

12. 11
 Scattering - Scattering is the redirection of EM energy by particles
suspended in the atmphere. It is dependant upon the number of particles
present in the atmosphere, the size of the particles, the wavemlength of
incoming radiation and the depth of atmosphere that the radiation must
travel through.
Particles that are small relative to the wavelength of incoming radiation
create rayleigh scattering. Rayleigh scattering is wave length dependant,
favoring short wavelengths, ansd is responsible for our sky appearing blue.
Mie scattering is produced by particles having diameter approzimately
equal to the wavelength of the imcoming radiation. Mie scattering is
typically created by dust, smoke, haze and water droplets in the lower
atmosphere.
The scattering produced by very large particles relative to the incoming
radiation is nonselective. As the name implies, nonselective scattering is
not wavelength dependant and scatters all wavelengths equally.
Absorption - Absorption occurs when atmospheric particles do not allow
EM radiation to be fully transmitted. The amount of energy absorbed is
dependant upon the absorber and the wavelength of incoming radiation.
Energy that is absorbed is then re-emitted at a longer wavelengths, There
are three gasses in the atmosphere that are responsible for most of the
absorption in the earth's atmosphere.

13. 12
CO2 - Carbon Dioxide is concentrated in the lower atmosphere at
approximately .036% by volume of the the earth's atmosphere at sea level.
Interestingly, this amount is on the rise apprarently because of mankinds
burning of fossil fuels.
O3 - Ozone is concentrated in the upper stratoshpere and at ground levels
with concentrations of .07 ppm and .1 to .2 ppm respectively. Ozone is
important because it is responsible for much of the absorption of the high
energy, short wavelenght UV solar radiation from entering the Earth's
lower atmosphere. (ozone hole and importance of lower atmos O3)
H2O - Water vapor varies dramatically throughout the Earth's atmosphere
and therefore the role of H2O as an absorber of EM radiation varies with
time and location.
There are other items in the atmosphere that play an important role in the
absorption of incoming solar radiation. These include methane (CH4),
Nitrous Oxice (NO), and clorofluorocarbons (CFCs).
Refraction - Refraction is the deflection of EM radiation as it passes from
one medium with one refractive index to a medium with a different
refractive index. Refractive index is defined asthe ratio or the speed of light
in a vacume to the speed of light in the medium and is calculated by:
In the Earth's atmosphere temperature, compostition and humidity all affect
the density which affect the refractive index. The angle that the radiation
will be bent is defined by Snells Law:

14. 13
The direction that it is bent is determined by the density of the two
mediums. If the energy is passing into a more dense medium, then the
energy is deflected toward the surface normal (a line drawn perpendicular
to the surface separating the two mediums).
Conclusion
There are more electromagnetic waves than the sunlight. Examples are the
short-wavelength gamma radiation or the long-wavelength radio waves.
The different electromagnetic waves are classified within the
electromagnetic spectrum according to their wavelengths and frequencies.
The wavelength which can pass through the atmosphere. The foundation of
remote sensing technology is based on the measurement and interpretation
of the patterns of EMR. EMR is a dynamic form of energy. EMR transmit
cross space in the wave form and in the speed of light.

15. 14
Reference
1https://www.researchgate.net/publication/301529214_Electromagneti
c_Spectrum_and_Remote_Information
2http://www.geo.mtu.edu/volcanoes/vc_web/background/b_
remote_sensing.html#:~:text=Stefan-
Boltzmann%2520Law%2520states%2520that,emitted%2520radi
ation%2520is%2520calculated%25
3http://www.fis.uni-
bonn.de/en/recherchetools/infobox/beginners/what-remote-
sensing/electromagnetic-
spectrum#:~:text=Conclusion%3A,to%20their%20wavelengths%20and
%20frequencies
4https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_
Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Th
eoretical_Chemistry)/Spectroscopy/Fundamentals_of_Spectroscopy/El
ectromagnetic_Radiation
5http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson1-
2/index.html