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1. •Definitions,Principle,Varioustypesofsurveying-
Basedonmethodsandinstruments,
•Classifications,uses,necessityanduseofvarious
scalesandverniers
•Differenttypesofranging,tapes,chains,linear
measurements,approximate,direct,opticaland
electronicmethods,ChainSurveying,Minor
Instrumentsforsettingoutrightangle.

2. Surveying
•“Surveyingistheartofandscienceof
determiningtherelativepositionsofvarious
pointsorstationsonthesurfaceoftheearthby
measuringthehorizontalandvertical
distances,angles,andtakingthedetailsof
thesepointsandbypreparingamaporplanto
anysuitablescale.

3. Objective ofSurveying
•Theobjectofsurveyingistoprepareamapor
plantoshowtherelativepositionsofthe
objectsonthesurfaceoftheearth.Themapor
planisdrawntosomesuitablescale.Italso
showsboundariesofdistrictsstates,and
countriestoo.Itfeaturesdifferentengineering
buildingroadsrailwaysdamscanalsetc.

4. Objective ofSurveying

5. Objective ofSurveying

6. Uses ofSurveying
Thesurveyingmaybeusedfor following purposes:
•Toprepareatopographicalmapwhichshowshills,
valleys,rivers,forests,villages,townsetc.
•Toprepareacadastralmapwhichshowsthe
boundariesoffields,plots,housesandother
properties..
•Toprepareanengineeringmapwhichshowsthe
positionofengineeringworkssuchasbuildings,
roads,railways,dams,canals.

7. Uses ofSurveying
•Toprepareacontourmaptoknow the topography of
the area to find out the best possible site for roads,
railways, bridges, reservoirs, canals,etc.
•Surveyingisalsousedtopreparemilitarymap,
geologicalmap,archaeologicalmapetc.
•Forsettingoutworkandtransferringdetailsfromthe
mapontheground.

8. Primary Divisions ofSurveying
Weknowthattheshapeoftheearthisspheroidal.
Thusthesurfaceisobviouslycurved.Surveyingis
primarilydividedintotwotypesconsideringthe
curvatureoftheearthssurface.
•PlaneSurveying
•GeodeticSurveying

9. Primary Divisions ofSurveying
•PlainSurveying
•Theplainsurveyingisthattypeofsurveyinginwhich
earthsurfaceisconsideredasaplaneandthe
curvatureoftheearthisignored.Insuchsurveyinga
linejoininganytwostationsisconsideredtobe
straight.Thetriangleformedbyanythreepointsis
consideredasaplanetriangle,andtheanglesofthe
triangleareconsideredasplainangles.
•Surveyingiscarriedoutforasmallareaoflessthan
250km
2.Itiscarriedoutbylocalorstateagencies
likeR&Bdepartment,Irrigationdepartment,
Railwaydepartment.

10. PlainSurveying

11. Primary Divisions ofSurveying
GeodeticSurveying
•ThegeodeticSurveyingisthattypeofsurveyingin
whichthecurvatureoftheearthistakeninto
account.Itisgenerallyextendedoverlargerareas.
Thelinejoininganytwostationsisconsideredas
curvedline.Thetriangleformedbyanythreepoints
isconsideredtobesphericalandtheanglesofthe
triangleareconsideredtobesphericalangles.
Geodeticsurveyingisconductedbythesurveyof
IndiaDepartmentandiscarriedoutforalargerarea
exceeding250km
2

12. GeodeticSurveying

13. GeodeticSurveying

14. Plain Surveying VsGeodetic
Surveying
No.PlainSurveying GeodeticSurveying
1 The earth surface is consideredas
plainSurface.
The earth surface is consideredas
CurvedSurface.
2. The Curvature of the earthis
ignored
The curvature of earth is takeninto
account.
3 Line joining any two stationsis
considered to bestraight
The line joining any two stationsis
considered asspherical.
4. The triangle formed by anythree
points is considered asplain
The Triangle formed by any threepoints
is considered asspherical.
5. The angles of triangle are
considered as plainangles.
The angles of the triangle areconsidered
as sphericalangles.
6. Carried out for a small area <250
km
2
Carried out for a small area > 250km
2

15. Fundamental Principles of Surveying
•Twobasicprinciplesofsurveyingare:
•Alwaysworkfromwholetothepart,and
•Tolocateanewstationbyatleasttwomeasurements
(Linearorangular)fromfixedreferencepoints.

16. Fundamental Principles of Surveying
Alwaysworkfromwholetothepart:
•Accordingtothefirstprinciple,thewholesurvey
areaisfirstenclosedbymainstations(i.e..Control
stations)andmainsurveylines.Theareaisthen
dividedintoanumberofdivisionsbyformingwell
conditionedtriangles.

17. Work from Whole to thePart

18. Fundamental Principles of Surveying
•Themainsurveylinesaremeasuredvery
accuratelywithprecisesurveyinstruments.
Theremainingsidesof
measured.Thepurposeofthismethod of working
Thetriangleare
istocontrolaccumulationoferrors.During
measurement,ifthereisanyerror,thenitwillnot
affectthewholework,butifthereverseprocessis
followedthentheminorerrorinmeasurementwillbe
magnified.

19. Fundamental Principles of Surveying
•Tolocateanewstationbyatleasttwomeasurements
(Linearorangular)fromfixedreferencepoints.
•Accordingtothesecondprinciplethepointsare
locatedbylinearorangularmeasurementorbyboth
insurveying.Iftwocontrolpointsareestablished
first,thenanewstationcanbelocatedbylinear
measurement.LetA&Barecontrolpoints,anew
pointCcanbeestablished.

20. Fundamental Principles of Surveying
•Following are the methods of locating point C
from such reference points A &B.
•The distance AB can be measured accuratelyand
the relative positions of the point can be then
plotted on the sheet to somescale.
(a) Taking linear measurement from A and Bfor C.
(b) Taking linear measurement of perpendicular
from D to C.
•(c) Taking one linear measurement from B and
one angularmeasurementas∕ABC

21. Fundamental Principles of Surveying
•Taking two angular measurement at A & Bas
angles / CAB and /ABC.
•Taking one angle at B as / ABC and onelinear
measurement from A asAC.

22. Fundamental Principles of
Surveying

23. Leveling
•Levelingisabranchofsurveyingwhichdealswith
themeasurementofrelativeheightsofdifferent
pointson,aboveorbelowthesurfaceoftheearth.
Thusinleveling,themeasurements(elevations)are
takenintheverticalplane.

24. Leveling

25. Leveling

26. Classification ofSurveying
•Surveycanbeclassifiedintovarious
categoriesdependingonmethodsusedand
natureofthefield.
•ClassificationBasedonInstruments.
•ChainSurvey:
•Thisisthesimplesttypeofsurveyinginwhich
onlylinearmeasurementsaremadewitha
chainoratape.Angularmeasurementsarenot
taken.

27. ChainSurvey

28. Classification ofSurveying
•CompassSurvey:
•InCompassSurvey,theanglesare measured
with the help of a magneticcompass.
•Chain and compasssurvey:
•Inthissurveylinearmeasurementsaremade
withachainoratapeandangular
measurementswithacompass.

29. CompassSurvey

30. CompassSurvey

31. CompassSurvey

32. Classification ofSurveying
•PlaneTableSurveying
•Itisagraphicalmethodofsurveyinginwhich
fieldworksandplottingbotharedone
simultaneously.
•TheodoliteSurvey:
•Intheodolitesurveythehorizontalanglesare
measuredwiththetheodolitemoreprecisely
thancompassandthelinearmeasurementsare
madewithachainortape.

33. Plane TableSurveying

34. Plane TableSurveying

35. Plane TableSurveying

36. TheodoliteSurvey

37. TheodoliteSurvey

38. Classification ofSurveying
•TachometrySurvey:
•Aspecialtypeoftheodoliteknownas
tachometerisusedtodeterminehorizontaland
verticaldistancesindirectly.
•LevelingSurvey:
•Thistypeofsurveyisusedtodeterminethe
verticaldistances(elevations)andrelative
heightsofpointswiththehelpofaninstrument
knownaslevel.

39. TachometrySurvey

40. TachometrySurvey

41. TachometrySurvey

42. LevelingSurvey

43. Classification ofSurveying
•ClassificationBasedonmethods.
Triangulation:
•Triangulationisbasicmethodofsurveying,whenthe
areatobesurveyedislarge,triangulationisadopted.
Theentireareaisdividedintonetworkoftriangles.
Traversing:
•ATraversingiscircuitofsurveylines.Itmaybeopen
orclosed.Whenthelinearmeasurementsaredone
withachainandatapeandthedirectionsor
horizontalanglesaremeasuredwithacompassora
theodoliterespectivelythesurveyiscalled
traversing.

44. Triangulation

45. Traversing

46. Classification ofSurveying
•ClassificationbasedonPurpose
•GeologicalSurvey:
•Inthisbothsurfaceandsubsurfacesurveyingare
conductedtolocatedifferentmineralsandrocks.In
addition,geologicalfeaturesoftheterrainsuchas
foldsandfaultsarelocated.

47. GeologicalSurvey
HydrologicalMaps
GeologicalMaps

48. Classification ofSurveying
MineSurvey
•MineSurveyincludesincludebothsurfaceand
undergroundsurveys.Itisconductedforthe
explorationofmineraldepositsandtoguide
tunnelingandotheroperationsassociatedwith
mining.

49. MineSurvey

50. Classification ofSurveying
•ArchaeologicalSurvey
•Itisconductedtolocaterelicsofantiquity,
civilization,kingdoms,forts,temples,etc.
•MilitarySurvey
•Ithasaveryimportantandcriticalapplicationsinthe
military.Aerialsurveysareconductedforthis
purpose.Itisconductedtolocatestrategicpositions
forthepurposeofarmyoperations.

51. ArchaeologicalSurvey

52. MilitarySurvey

53. Classification ofSurveying
•ClassificationbasedonNatureoffield
•LandSurvey
•LandSurveyisdoneonlandtoprepareplanand
mapsofagivenarea.Topographical,cityand
cadastralsurveysaresomeoftheexamplesofland
surveying.
•HydrologicalSurveying
•Thissurveyisconductedonornearthebodyof
watersuchaslake,river,coastalarea.ThisSurvey
consistsoflocatingshorelinesofwaterbodies.

54. LandSurvey

55. HydrologicalSurveying
HydrologicalMaps
HydrologicalMaps

56. Classification ofSurveying
•AstronomicalSurvey
•Thissurveyisconductedforthedeterminingof
latitudes,longitudes,azimuths,localtime,etc.for
variousplacesonearthbyobservingheavenlybodies
(sunorthestars).
•AerialSurvey
•Anaerialsurveyisconductedfromaircraft.Aerial
camerastakephotographsofthesurfaceoftheearth
inoverlappingstripsofland.Thisisalsoknownas
photographicsurvey.

57. AstronomicalSurvey

58. AstronomicalSurvey

59. AstronomicalSurvey

60. AerialSurvey

61. Plan andMaps
•Oneofthebasicobjectiveofsurveyingistoprepareplans
andmaps.
•Plan
•Aplanisthegraphicalrepresentationtosomescale,ofthe
featureson,nearorbelowthesurfaceoftheearthas
projectedonahorizontalplane.Thehorizontalplaneis
representedbyplaneofdrawingsheetsonwhichtheplanis
drawntosomescaleHoweverthesurfaceoftheearthis
curveditcannotbetrulyrepresentedonaplanewithout
distortion.Inplanesurveyingtheareainvolvedaresmall,
theearth‟ssurfacemaybeconsideredasplaneandhence
planisconstructedbyorthographicprojections.Aplanis
drawnonarelativelylargescale.

62. Plan andMaps
•Map
•Ifthescaleofthegraphicalprojectionona
horizontalplaneissmall,theplaniscalledamap.
Thusgraphicalrepresentationiscalledaplanif
thescaleislargewhileitiscalledamapifthe
scaleissmall.
•Onplan,generallyonlyhorizontaldistancesand
directionsoranglesareshown.Ontopographical
map,howevertheverticaldistances(elevations)
arealsorepresentedbycontourlines.

63. WHAT IS CHAIN SURVEING ?
•Chain surveying is the type of surveying in
which only linear measurements are
takenin thefield.
•This type of surveying is done for surveys of
small extent to describe the boundaries of
plot oflandtolocatetheexistingfeatures
onthem.

66. PRINCIPAL OF CHAIN SURVEYING
The principal of chain surveying is to divide the
area into a number of triangles of suitable sides.
As a triangles is the only simple plane of
geometrical figure which can be plotted from the
lengths of the three sides even if the angels are
not known.

67. A network of triangles (triangulation)is
preferred to in chain surveying.
If the area to be surveyed is triangular in shape
and if the lengths and sequenceof its three
sides are recorded the plane of area can be easily
drawn.

68. TERMS RELATED WITH CHAIN SURVEYING

69. SURVEYSTATIONS
Survey stations are the points at thebeginning
and at the end of the chain line.They may also
occur at any convenient position on the chain
line. Such stations may be:
Main stations
Subsidiary stations
Tie stations

70. (1) Main stations:
Stations taken along the boundary of an
area as controlling points known as ‘main
stations’.
The lines joining the main stations arecalled
‘main survey lines’. The main survey lines
should be cover the whole area to be
surveyed.The main stations are denotedby
withletters A,B,C,D,etc.

72. (2) Subsidiary stations:
Stationswhichareonthemainsurveylinesor
anyothersurveylinesareknownas‘Subsidiary
stations’.Thesestationsaretakentorunsubsidiary
linesfordividingtheareaintotriangles,for
checkingtheaccuracyoftrianglesandforlocating
interiordetails.thesestationsaredenotedby‘‘
withlettersS
1,S
2,S
3,etc.

73. (3) Tie stations :
Thesearealsosubsidiarystationstakenonthe
mainsurveylines.Linesjoiningthetiestationsare
knownas‘tielines’.Tielinesaretakentolocate
interiordetails.Thestationsaredenotedby‘’
withlettersT
1,T
2,T
3,etc.

74. (4) BASE LINE:
Thelineonwhichtheframeworkofthesurveyis
builtisknownasthe‘baseline’.Itisthemost
importantlineofthesurvey.Generally,the
longestofthemainsurveylineisconsideredas
thebaseline.Thislineshouldbemeasuredvery
carefullyandaccurately.Infig.BDisthebase
line.

75. (5) CHECK LINE:
Thelinejoiningtheapexpointofatriangletosome
fixedpointsonitsbaseisknownasthe‘checkline’.
Itistakentochecktheaccuracyofthetriangle.
Sometimesthislineishelpstolocateinteriordetails
.Infig.CS
1,AS
2arethechecklines.

76. (6) TIE –LINE:
A line joining tie stations is termed as a tie line.
It is run to take the interior details which are
far away from the main lines and also to avoid
long offsets. It can also serve as check line. In
Fig. T
1 T
2 is the tieline.

77. INTERACTION OF EMR WITHATMOSPHERE AND EARTHSURFACE
Electro-magneticradiation(EMR)orenergyinteractionswithatmosphereandwiththeearthsurface
playavitalroleinremotesensing.Energyinteractionswiththeatmospheredictatethespectral
regionsthroughwhichonlywecandotheremotesensingwhichareknownasspectralwindows(the
spectralregionswhereatmosphereismoreorlesstransparent).
ENERGY INTERACTION INATMOSPHERE
Irrespectiveofitssource,allradiationdetectedbyremotesensorspassesthroughsomedistance,or
pathlength,ofatmosphere.Thepathlengthinvolvedcanvarywidely.Forexample,space
photographyresultsfromsunlightthatpassesthroughthefullthicknessoftheearth'satmosphere
twiceonitsjourneyfromsourcetosensor.Ontheotherhand,anairbornethermalsensordetects
energyemitteddirectlyfromobjectsontheearth,soasingle,relativelyshortatmosphericpath
lengthisinvolved.
Because of the varied nature of atmospheric effects, we treat thissubject on a sensor-by-sensor. The
atmosphere can
haveaprofoundeffecton,amongotherthings,theintensityandspectralcompositionofradiation
availabletoanysensingsystem.Theseeffectsarecausedprincipallythroughthemechanismsof
atmosphericscatteringandabsorption.
(A).SCATTERING:
Atmosphericscatteringisunpredictablediffusionofradiationbyparticlesintheatmosphere.
Scatteringistheprocesswhereanatom,moleculeorparticleredirectsenergy.

78. TYPES OFSCATTERING
1.Rayleigh scattering –atmosphericatom
2.Mie scattering –aerosol
3.Non selective scattering –cloud

79. Rayleighscattering:
AtmosphericgasorsmallmoleculescattersradiationbyaprocessknownasRayleighscattering.Rayleigh
scatteriscommonwhenradiationinteractswithatmosphericmoleculesandothertinyparticlesthatare
muchsmallerindiameterthanthewavelengthoftheinteractingradiation.TheeffectofRayleighscatteris
inverselyproportionaltothefourthpowerofwavelength.
Rayleighscatteringredirectstheradiationaboutequalinalldirection.Rayleighscatteringisresponsiblefor
blueskiesandredsunsets.
Miescattering:
AnothertypeofscatterisMiescatter,whichexistswhenatmosphericparticlediametersessentiallyequal
theenergywavelengthsbeingsensed.WatervapouranddustaremajorcausesofMiescatter.Thistypeof
scattertendstoinfluenceslongerwavelengthscomparedtoRayleighscatter.AlthoughRayleighscatter
tendstodominateundermostatmosphericconditions,Miescatterissignificantinslightlyovercastones.
Examples:watervapor,smokeparticles,finedust

80. Nonselectivescattering:
Amorebothersomephenomenonisnonselectivescatter,whichcomesabout
whenthediametersoftheparticlescausingscatteraremuchlargerthanthe
energywavelengthsbeingsensed.Waterdroplets,forexample,causesuch
scater.Theycommonlyhaveadiameterinthe5to100µm(mocrometer,10-
6m)rangeandscatterallvisibleand
ReflectedIRwavelengthsaboutequally.Consequently,thisscatteringis
"nonselective"withrespecttowavelength.
Inthevisiblewavelengths(Approx.0.4to0.7µm),equalquantitiesofblue,
green,andredlightarescattered,Makingfogandcloudsappearwhite.
Examples:waterdroplets,icecrystals,volcanicash,Smog

81. (B).ABSORPTION
Atmosphericabsorptionresultsintheeffectivelossofenergy
toatmosphericconstituents.Thisnormallyinvolves
absorptionofenergyatagivenwavelength.Themost
efficientabsorbersofsolarradiationinThisregardiswater
vapour,carbondioxide,andozone.Becausethesegassestend
toabsorbelectromagneticEnergyinspecificwavelength
bands,theystronglyinfluence"wherewelook"spectrally
withanygivenremoteSensingsystem.Thewavelength
rangesinwhichtheatmosphereisparticularlytransmissive
ofenergyarereferredtoasatmosphericwindows.

82. (C).TRANSMISSION:
Amaterialtransmitslightwhenitallowsthelighttopassthroughit.Transparentmaterialsallowallthelighttopass
throughthemsothatyoucaneasilyseewhatisontheotherside.Examplesoftransparentmaterialsareglass,water,
andair.Translucentmaterialsscatterthelightthatpassesthroughthem.Youcantellthatsomethingisontheother
side,butyoucannotseedetailsclearly.Examplesoftranslucentmaterialsarewaxpaper,frostedglass,andsome
kindsofplastic.Iftheobjectistransparent,thenthevibrationsoftheelectronsarepassedontoneighboringatoms
throughthebulkofthematerialandreemittedontheoppositesideoftheobject.Suchfrequenciesoflightwavesare
saidtobetransmitted.Iftheobjectisopaque,thenthevibrationsoftheelectronsarenotpassedfromatomtoatom
throughthebulkofthematerial.Rathertheelectronsofatomsonthematerial'ssurfacevibrateforshortperiodsof
timeandthenreemittheenergyasareflectedlightwave.Suchfrequenciesoflightaresaidtobereflected.

83. INTERACTIONS WITH EARTH SURFACEFEATURES
Electromagneticradiationthatpassesthroughtheearth'satmospherewithoutbeing
absorbedorscatteredreachestheearth'ssurfacetointeractindifferentwayswithdifferent
materialsconstitutingthesurface.Whenelectromagneticenergyisincidentonanygiven
earthsurfacefeature,threefundamentalenergyinteractionswiththefeaturearepossible.
Therearethreewaysinwhichthetotalincidentenergywillinteractwithearth'ssurface
materials.Theseare
Absorption
Transmission,and
Reflection
Absorption(A)occurswhenradiation(energy)isabsorbedintothetargetwhile
transmission(T)occurswhenradiationpassesthroughatarget.Reflection(R)occurswhen
radiation"bounces"offthetargetandisredirected.
How much of the energy is absorbed, transmitted or reflected by a material will depend
upon:
•Wavelength of theenergy
•Material constituting the surface,and
•Condition of thefeature.

84. Reflection from surfaces occurs in twoways:
1.When the surface is smooth, we get a mirror-like or smooth reflection where all
(or almost all) of the incident energy is reflected in one direction. This is called
Specular Reflection and gives rise toimages.
2.When the surface is rough, the energy is reflected uniformly in almost all
directions. This is called Diffuse Reflection and does not give rise toimages.
SpecularReflectionDiffuseReflection
Mostsurfacefeaturesoftheearthliesomewherebetweenperfectlyspecularorperfectlydiffuse
reflectors.Whetheraparticulartargetreflectsspecularlyordiffusely,orsomewhereinbetween,
dependsonthesurfaceroughnessofthefeatureincomparisontothewavelengthoftheincoming
radiation.

85. Ifthewavelengthsaremuchsmallerthanthesurfacevariationsortheparticle
sizesthatmakeupthesurface,diffusereflectionwilldominate.Forexample,
fine-grainedsandwouldappearfairlysmoothtolongwavelength
microwavesbutwouldappearquiteroughtothevisiblewavelengths.
Vegetation:
A chemical compound in leaves called chlorophyll strongly absorbs radiation in the
red and blue wavelengths but reflects greenwavelengths.
Leavesappear"greenest"tousinthesummer,whenchlorophyllcontentisat
itsmaximum.Inautumn,thereislesschlorophyllintheleaves,sothereis
lessabsorptionandproportionatelymorereflectionoftheredwavelengths,
makingtheleavesappearredoryellow(yellowisacombinationofredand
greenwavelengths).

86. Theinternalstructureofhealthyleavesactasexcellent
diffusereflectorsofnear-infraredwavelengths.Ifour
eyesweresensitivetonear-infrared,treeswouldappear
extremelybrighttousatthesewavelengths.Infact,
measuringandmonitoringthenear-IRreflectanceisone
waythatscientistscandeterminehowhealthy(or
unhealthy)vegetationmaybe.
Water:
Longerwavelengthvisibleandnearinfraredradiationis
absorbedmorebywaterthanshortervisiblewavelengths.Thus
watertypicallylooksblueorblue-greenduetostronger
reflectanceattheseshorterwavelengths,anddarkerifviewedat
redornearinfraredwavelengths.

87. Ifthereissuspendedsedimentpresentintheupperlayersofthewaterbody,thenthiswillallow
betterreflectivityandabrighterappearanceofthewater.
Theapparentcolourofthewaterwillshowaslightshifttowardslongerwavelengths.
Suspendedsediment(S)canbeeasilyconfusedwithshallow(butclear)water,sincethesetwo
phenomenaappearverysimilar.
Chlorophyllinalgaeabsorbsmoreofthebluewavelengthsandreflectsthegreen,makingthewater
appearmoregreenincolourwhenalgaeispresent.
Thetopographyofthewatersurface(rough,smooth,floatingmaterials,etc.)canalsoleadto
complicationsforwater-relatedinterpretationduetopotentialproblemsofspecularreflectionand
otherinfluencesoncolourandbrightness.
Wecanseefromtheseexamplesthat,dependingonthecomplexmake-upofthetargetthatisbeing
lookedat,andthewavelengthsofradiationinvolved,wecanobserveverydifferentresponsestothe
mechanismsofabsorption,transmission,andreflection.

88. Spectral Response ofMaterials:
By measuring the energy that is reflected (or emitted) by targets on the Earth's surface over a
variety of different wavelengths, we can build up a spectral response for that object. The spectral
response of a material todifferentwavelengths of EMR can be represented graphically as a
Spectral ReflectanceCurve.
Itmaynotbepossibletodistinguishbetweendifferentmaterialsif
weweretocomparetheirresponseatonewavelength.Butby
comparingtheresponsepatternsofthesematerialsoverarangeof
wavelengths(inotherwords,comparingtheirspectralreflectance
curves),wemaybeabletodistinguishbetweenthem.Forexample,
waterandvegetationmayreflectsomewhatsimilarlyinthevisible
wavelengthsbutarealmostalwaysseparableintheinfrared.
•Spectral response can be quite variable, even for the same target
type, andcanalso vary with time (e.g. "green-ness" of leaves) and
location.

89. ELECTROMAGNETICSPECTRUM

90. Electromagneticspectrum
•Distributionofthecontinuumofallradiantenergiescan
beplottedeitherasafunctionofwavelengthorof
frequencyinachartknownastheelectromagnetic
spectrum
•Itrangesfromshorterwavelengths(includingX-raysand
gammarays)tolongerwavelengths(microwavesand
radiowaves)

92. •electromagneticspectrumistherangeofall
possiblefrequenciesofelectromagnetic
radiation
•EMRextendsoverawiderangeofenergiesor
wavelengthsorfrequencies

93. •Radio:Yourradiocapturesradiowavesemittedbyradio
stations,bringingyourfavoritetunes.Radiowavesarealso
emittedbystarsandgasesinspace.
•Microwave:Microwaveradiationwillcookyourpopcornin
justafewminutes,butisalsousedbyastronomerstolearn
aboutthestructureofnearbygalaxies.
•Infrared:Nightvisiongogglespickuptheinfraredlight
emittedbyourskin.Inspace,infraredlighthelpsusmapthe
dustbetweenstars.

94. •Ultraviolet:UltravioletradiationisemittedbytheSunandarethe
reasonskintansandburns."Hot"objectsinspacealsoemitUV
radiation
•X-ray:AdentistusesX-raystoimageyourteeth,andairport
securityusesthemtoseethroughyourbag.Hotgasesinthe
UniversealsoemitX-rays
•Gammaray:Doctorsusegamma-rayinthetreatmentof
dangerousdiseases.

95. The electromagneticspectrum

97. •EMRintherangeof0.4µmto0.7µmis
known as the visibleregion
•white light contains a mix of allwavelengths in
the visibleregion

98. Visible portion ofspectrum
•Violet:
•Blue:
•Green:
•Yellow:
•Orange:
•Red:0.620 µm to 0.7µm
0.4 µm to 0.446µm
0.446 µm to 0.500µm
0.500 µm to 0.578µm
0.578 µm to 0.592µm
0.592 µm to 0.620µm
Among these blue, green and red arethe primarycolors

99. •SirIsaacnewton 1666 passed white light through a glass
prism and concluded that white light is a mixture of several
other lights

100. •Theprinciplebehindthisisthatasradiation
passesfromonemediumtoanotheritbendsthis
phenomenoniscalledrefractiveindex

101. •Theprocessofseparatingtheconstituent
colours in white light is knownas dispersion

102. •The lightwhich our eyes, our sensors can detect is part
of the visible spectrum
•Some remote sensing instruments also detects radiations
invisible to our eyes.
•Range of visible wavelength is from 0.4 µm to 0.7 µm
•Longest visible wavelength is red and shortest is violet
•Apart from these three, all other colorscan be formed by
combining blue, green and red in various proportions
•EM spectrum spreads from cosmic rays to radio waves
•Region of EM spectrum useful in remote sensing is from
ultra violet to microwave

103. USES
•Mostpartsoftheelectromagneticspectrumareusedin
scienceforspectroscopicandotherprobinginteractions,
aswaystostudyandcharacterizematter.
•Inaddition,radiationfromvariouspartsofthespectrum
hasfoundmanyotherusesforcommunicationsand
manufacturing