Presented by Rehana Jamal Dated :29/10/14 Database Management System & Applications of Remote sensing and GIS Subject Lecture# 2 P1 “Characteristics of Electromagnetic radiation” “Wavelength regions of electro-magnetic radiation” Topics 29/10/14 1

2 Characteristics of Electromagnetic radiation Electromagnetic Energy can be modelled in two ways i. By waves ii. By Photons(Energy bearing particles) Velocity of light, c Distance Electromagnetic waves consist of a combination of oscillating electrical and magnetic fields, perpendicular to each other. 29/10/14

3 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*10 8 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 29/10/14

4 / Crest Velocity of light, c 29/10/14

5 f or V = c/ Relation between the speed of light (c), wavelength ( ), and frequency (f or V ): Thus, there is an inverse relationship between wavelength and frequency 29/10/14

6 Thus (frequency [f/V] * wavelength[lambda]) is equal to a constant (c) Relation between the speed of light (c), wavelength ( ), and frequency (f or V ): 29/10/14

7 Sources of electromagnetic radiation  Sources of long wavelengths  Sources of visible light  Sources of short wavelength  Detectors of electromagnetic radiation 29/10/14

8 Note the trends: bluer light has shorter wavelength, higher frequency, and more energy. Redder light has longer wavelength, lower frequency, and less energy. 29/10/14

9 UnitSymbolLength (m)Type of Radiation AngstromÅ X-ray Nanometernm10 -9 UV, visible Micrometerµm10 -6 Infrared Millimetermm10 -3 Infrared Centimetercm10 -2 Microwave Meterm1TV, radio The unit of length chosen to describe a particular wavelength is typically dependent on the type of electromagnetic radiation 29/10/14

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. Types of Energy Resources 10 29/10/14

11 In respect to the type of Energy Resources Passive Remote Sensing 29/10/14

12 In respect to the type of Energy Resources Passive Remote Sensing 29/10/14

13 In respect to the type of Energy Resources: Active Passive remote Sensing 29/10/14

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. Electro-Magnetic Spectrum (EMS) 14 Wavelength regions of electro-magnetic radiation 29/10/14

15 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. 29/10/14

Optical wavelength Reflective portion (i) Visible (ii) Near IR (iii) Middle IR Far IR (Thermal, Emissive) Wavelength(mm) Name 16 29/10/14

17 In respect to Wavelength Regions Visible and Reflective Infrared Remote Sensing Thermal Infrared Remote Sensing Microwave Remote Sensing 29/10/14

18 29/10/14 (1mm)

19 29/10/14 Summary

References: Principles of Remote sensing edited by Lucas L.E. Janssen 20 29/10/14

21 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