Download ELECTROMAGNETIC WAVES

MAXWELL’S EQUATIONS
ELECTROMAGNETIC WAVES
 JAMES CLARK MAXWELL OF SCOTLAND GAVE A
SET OF FORMULAE FOR ELECTRIC CHARGE,
CURRENT AND THEIR ELECTRIC FIELD AS WELL
AS MAGNETIC FIELD.
 THESE FORMULAE EMPHASIZE ON THE INTER
RELATION BETWEEN ELECTRICITY AND
MAGNETISM.
 MAXWELL HAS GIVEN FOUR EQUATIONS
CONNECTING MAGNETIC FIELD AND ELECTRIC
FIELD.
 AMPERE-MAXWELL CIRCUITAL LAW:

𝐵. 𝑑𝑙 = 𝜇 𝑜 𝐼𝑐 + 𝜖𝑜 µ 𝑜
𝑑∅ 𝐸
𝑑𝑡
 GAUSS LAW OF ELECTROSTATICS:

𝐸. 𝑑𝑆 = 𝑄/∈ 𝑜
 GAUSS LAW FOR MAGNETISM:

𝐵. 𝑑𝑆 = 0
 FARADAY’S LAW OF ELECTROMAGNETIC
INDUCTION:

𝐸. 𝑑𝑙 = −
𝑑∅ 𝐵
𝑑𝑡
BASIC SOURCES OF
ELECTROMAGNETIC WAVES
 A CHARGE OSCILLATING HARMONICALLY IS A
SOURCE OF ELECTROMAGNETIC WAVE OF SAME
FREQUENCY.
 H.R. HERTZ EXPERIMENT CONFIRMED THE FACT
THAT A VIBRATING ELECTRIC CHARGE RADIATES
ELECTROMAGNETIC WAVES.
SOURCE OF EM WAVES
 LATER ON J.C.BOSE HAS SUCCESSFULLY
PRODUCED ELECTROMAGNETIC WAVES IN HIS
LABORATORY IN CALCULLTA AFTER 8 YEARS.
 IN 1895, MARCONI MADE AN IMPORTANT
DISCOVERY WHICH LED TO THE COMMERCIAL
USE OF EM WAVES IN THE FILED OF
COMMUNICATION.
CHARACTERISTIC PROPERTIES OF
ELECTROMAGNETIC WAVES
 EM WAVES DO NOT REQUIRE ANY MEDIUM FOR
PROPAGATION.
 SPEED OF EM WAVES IN FREE SPACE OR VACUUM IS
EQUAL TO 3 LAKH KM PER SECOND.
 C=
1
𝜇𝑜𝜖𝑜
 SPEED OF EM WAVES IN A MEDIUM IS GIVEN BY
 v=
1
𝜇𝜖
PROPERTIES OF EM WAVES
 EM WAVES ARE SELF SUSTAINING ELECTRIC AND
MAGNETIC FIELD OSCILLATIONS IN SPACE.
 EM WAVES ARE TRANSVERSE IN NATURE i.e. THE
ELECTRIC FIELD AND MAGNETIC FIELD ARE
PERPENDICULAR TO EACH OTHER AS WELL AS
PERPENDICULAR TO THE DIRECTION OF
PROPAGATION OF THEWAVE.
PROPERTIES OF EM WAVES
 THE AMPLITUDES OF ELECTRIC FIELD AND
MAGNETIC FIELD ARE RELATED TO EACH OTHER
BY A RELATION

c=
𝐸𝑜
𝐵𝑜
 EM WAVES CAN BE REFLECTED, REFRACTED AND
DIFFRACTED.
 EM WAVES SHOW THE PHENOMENON OF
INTERFERENCE.
PROPERTIES OF EM WAVES
 EM WAVES CAN BE POLARISED.
 EM WAVES ARE NOT DEFLECTED Y MAGNETIC
AND ELECTRIC FIELDS.
 INTENSITY OF AN EM WAVE DEPENDS UPON THE
AMPLITUDE OF ELECTRIC FIELD AND MAGNETIC
FIELD.
 EM WAVES TRANSPORT ENERGY.
ELECTROMAGNETIC SPECTRUM
REGIONS OF EM SPECTRUM
 AN EM SPECTRUM CONSISTS OF THE FOLLOWING




WAVES:
1. RADIO WAVES
2. MICRO WAVES
3. INFRARED WAVES 4. VISIBLE LIGHT
5. ULTRA-VIOLET WAVES
6. X – RAYS 7. GAMMA RAYS
RADIO WAVES
 WAVELENGTH RANGE: 0.3m TO 600nm
 FREQUENCY RANGE:
500kHz TO 1000MHz
 SOURCE: ACCELERATED CHARGED PARTICLES IN
A CONDUCTING WIRE OR CHANGING ELECTRIC
CURRENT IN LC CIRCUIT.
 USES: MAINLY USED IN RADIO AND TELEVISION
COMMUNICATION.
MICRO WAVES
 WAVELENGTH RANGE: 0.1m TO 1 mm
 FREQUENCY RANGE: 10 9 Hz TO 10 12 Hz
 SOURCE: Oscillating electrons in a cavity commonly
used oscillators to produce micro waves are Klystron,
Magnetron Gunn diodes.
 USES: USED IN RADAR SYSTEMS FOR AIRCRAFT
NAVIGATION.
 USED FOR ATOMIC AND MOLECULAR RESEARCH.
MICRO WAVES – USES
 USED IN MICRO WAVE OVENS FOR COOKING
AND WARMING OF FOOD.
 USED FOR COMMUNICATION BY CELLULAR
PHONES.
 USED IN WEATHER RADAR.
INFRA-RED(IR) WAVES
 WAVELENGTH RANGE: 1mm TO 700 nm
 FREQUENCY RANGE:10 11 Hz TO 10 14 Hz
 SOURCE: HOT BODIES(VIBRATIONS OF
ATOMS/MOLECULES)
 USES: These waves can pass through the haze, fog and
mist, so they are used in night vision devices during
warfare.
 Infra red detectors are used by earth satellites.
 Used to function the green houses because green
house gas and water vapours absorb the infrared waves
readily.
INFRA-RED WAVES
 USED IN REVEALING THE SECRET WRITINGS ON
THE ANCIENT WALLS
 INFRARED LAMPS ARE USED TO TREAT
MUSCULAR STRAINS.
 INFRARED REMOTES ARE USED TO OPERATE
ELECTRONIC DEVICES LIKE TV, VCD etc.
 THE INFRA-RED WAVES KEEP THE EARTH WARM.
VISIBLE LIGHT
 WAVELENGTH RANGE: 400 nm TO 780 nm
 FREQUENCY RANGE: 4 X 10 14 Hz TO 7 X 10 14 Hz
 SOURCE: JUMPING OF ELECTRON FROM HIGHER
ORBIT TO LOWER ORBIT OF AN ATOM
 USES:IT STIMULATES THE SENSE OF SIGHT IN
HUMAN BEINGS, SO THE BEAUTIFUL WORLD
AROUND US IS SEEN THE PRESENCE OF VISIBLE
LIGHT.
USES OF VISIBLE LIGHT
 IS USEFUL IN PHOTOGRAPHY
 IS USEFUL IN OPTICAL MICROSCOPY
 IS USEFUL IN ASTRONOMY
 IT IS A GREAT SOURCE OF ENERGY FOR HUMAN
LIFE.
ULTRA-VIOLET(UV) WAVES
 WAVELENGTH RANGE: 400 nm TO 0.6 nm
 FREQUENCY RANGE:7.5 X 10 14 Hz TO 5 X 10 15 Hz
 SOURCE: THE SUN, WELDING ARC, HIGH
VOLTAGE GAS DISCHARGE TUBE.
 USES:THEY ARE USED TO PRESERVE FOOD STUFF
AND MAKE DRINKING WATER FREE FROM
BACTERIA.
 USED FOR STERILIZING THE SURGICAL
INSTRUMENTS.
UV WAVES
 USED IN DETECTING THE INVISIBLE WRITINGS,
FORGED DOCUMENTS AND FINGER PRINTS.
 TO STUDY THE STRUCTURE OF MOLECULES.
 ARE USED IN LASIK EYE SURGERY AS UV WAVES
CAN BE FOCUSSED INTO A NARROW BEAMS.
X-RAYS
 WAVELENGTH RANGE:10 nm to 10 -4 nm
 FREQUENCY RANGE:10 18 Hz TO 10 20 Hz
 SOURCE:FAST MOVING ELECTRONS STRIKING A
TARGET OF HIGH AOMIC NUMBER.
 USES: USED IN MEDICAL DIAGNOSIS
 IN RADIO THERAPY TO CURE SKIN DISEASES,
CANCERS AND TUMORS.
 IN ENGINEERING FOR LOCATING FAULTS OR
CRACKS IN METALLIC MATERIALS.
GAMMA
RAYS
 WAVELENGTH RANGE:10
-10
m to 10 -14 m
 FREQUENCY RANGE:10 18 Hz TO 10 22 Hz
 SOURCE:RADIOACTIVE DECAY OF NUCLEI AND
NUCLEAR REACTIONS.
 USES:USED FOR TREATMENT OF CANCER.
 TO EXAMINE THE THICK MATERIALS FOR
STRUCTURAL FLAWS.
 FOR FOOD PRESERVATION.
EM WAVES
 THE END.