Transcript Wavelength regions of electro

Dated :29/10/14
Lecture# 2 P1
Subject
Database Management System &
Applications of Remote sensing and GIS
Topics
“Characteristics of Electromagnetic radiation”
“Wavelength regions of electro-magnetic radiation”
Presented by
Rehana Jamal
1
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Characteristics of Electromagnetic radiation
Electromagnetic Energy can be modelled in two ways
i. By waves ii. By Photons(Energy bearing particles)
Electromagnetic waves consist of a combination of oscillating
electrical and magnetic fields, perpendicular to each other.
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Characteristics of Electromagnetic radiation
It can travel through empty space.
The speed of light is constant in space.
A wavelength: Distance between crests or troughs through visible light
Velocity: 186,000 miles per second or300,000 kilometers per second or
299,790,000m/s or 3*108 m/s
Amplitude: The amplitude of electromagnetic waves relates to its intensity or
brightness(as in the case of visible light)
Frequency:
•The number of crests of the waves that pass by a point per second.
•Measured in units of hertz(Hz)
•1 hertz = 1 wave crest/second
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/ Crest
Velocity of light, c
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Relation between the speed of light (c),
wavelength ( ), and frequency (f or V ):
f
or
V = c/
Thus, there is an inverse relationship between wavelength and frequency
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Relation between the speed of light (c),
wavelength ( ), and frequency (f or V ):
Thus (frequency [f/V] * wavelength[lambda]) is equal to a constant (c)
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Sources of electromagnetic radiation

Sources of long wavelengths

Sources of visible light

Sources of short wavelength

Detectors of electromagnetic radiation
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Note the trends: bluer light has shorter wavelength, higher frequency, and more
energy. Redder light has longer wavelength, lower frequency, and less energy.
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The unit of length chosen to describe a particular wavelength is
typically dependent on the type of electromagnetic radiation
Unit
Symbol
Length (m)
Type of Radiation
Angstrom
Å
10-10
X-ray
Nanometer
nm
10-9
UV, visible
Micrometer
µm
10-6
Infrared
Millimeter
mm
10-3
Infrared
Centimeter
cm
10-2
Microwave
Meter
m
1
TV, radio
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Types of Energy Resources
In respect to the type of Energy Resources:
Passive Remote Sensing: Makes use of sensors that detect the
reflected or emitted electro-magnetic radiation from natural sources.
Active remote Sensing: Makes use of sensors that detect reflected
responses from objects that are irradiated from artificially-generated
energy sources, such as radar.
In respect to Wavelength Regions:
Visible and Reflective Infrared Remote Sensing.
Thermal Infrared Remote Sensing.
Microwave Remote Sensing.
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In respect to the type of Energy Resources
Passive Remote Sensing
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In respect to the type of Energy Resources
Passive Remote Sensing
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In respect to the type of Energy Resources:
Active Passive remote Sensing
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Wavelength regions of electro-magnetic radiation
Electro-Magnetic Spectrum (EMS)
Remote Sensing Technology makes use of the wide range of Electro-Magnetic
Spectrum (EMS) from a very short wave "Gamma Ray" to a very long 'Radio
Wave'.
Wavelength regions of electro-magnetic radiation have different names
ranging from Gamma ray, X-ray, Ultraviolet (UV), Visible light, Infrared (IR)
to Radio Wave, in order from the shorter wavelengths to the longer
wavelengths.
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Electromagnetic spectrum
Definition: “The range of wavelengths for electromagnetic waves--from the
very long to the very short--is called the Electromagnetic Spectrum”. It includes
following wavelengths bands:
•Radio and TV waves are the longest usable waves, having a wavelength of 1
mile (1.5 kilometer) or more.
•Microwaves are used in telecommunication as well as for cooking food.
•Infrared waves are barely visible. They are the deep red rays you get from a
heat lamp.
•Visible light waves are the radiation you can see with your eyes. Their
wavelengths are in the range of 1/1000 centimeter.
•Ultraviolet rays are what give you sunburn and are used in "black lights" that
make object glow.
•X-rays go through the body and are used for medical purposes.
•Gamma rays are dangerous rays coming from nuclear reactors and atomic
bombs. They have the shortest wavelength in the electromagnetic spectrum of
about 1/10,000,000 centimeter.
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Name
Optical wavelength
Reflective portion
(i) Visible
(ii) Near IR
(iii) Middle IR
Far IR (Thermal, Emissive)
Wavelength(mm)
0.30-15.0
0.38-3.00
0.38-0.72
0.72-1.30
1.30-3.00
7.00-15.0
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In respect to Wavelength Regions
Visible and Reflective Infrared Remote Sensing
Thermal Infrared Remote Sensing
Microwave Remote Sensing
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(1mm)
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Summary
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References:
•
www.google.com
•
www.wikipedia.com
•
Principles of Remote sensing
•
edited by Lucas L.E. Janssen
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Possible Exam Questions
Q1. Define the following:
 Visible spectram
 Infrared wavelength region
 Optical wavelength range
 Radio wave band
Q2.Differentiate the Passive remote sensing and Active remote
sensing.
5 Marks
Q3.Define Electromagnetic spectrum. Describe in detail the all
wavelength regions of electromagnetic spectrum. 15 Marks
Q5.Write a not on EM spectrum.
5 Marks
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