Sources of electromagnetic waves include the sun, radioactive substances, broadcast antennas, tungsten lamps, arc welding equipment, and medical appliances. EM waves are produced by oscillating electric and magnetic fields that propagate perpendicular to each other at a speed of 3x10^8 m/s. Scientists like Coulomb, Oersted, Ampere, Faraday, Maxwell, and Hertz contributed greatly to the understanding of electromagnetic waves through their discoveries and theories. The electromagnetic spectrum encompasses all types of EM waves ranging from gamma rays to radio waves, which are classified according to their wavelength and frequency.

1. Chapter – 4
Sources of Electromagnetic Waves

2. How You feel while sitting close to a fire ?
Sources
Sun Radiating Energy

3. Universe
Radioactive Substances

4. Broadcast TV antenna
Tungsten Lamp

5. Arc Welding
Medical Appliances

6. Historical Perspective of Electromagnetic Waves
EM waves are waves that are created as a result of vibrations
between an electric field and a magnetic field.
EM waves travel with a constant velocity of 3.00 x 108 ms-1 in
vacuum.
EM waves are transverse waves.
The electric field and magnetic field of an electromagnetic wave
are perpendicular (at right angles) to each other. They are also
perpendicular to the direction of the EM wave.
They can travel through air, liquid , a solid material or vacuum.

8. Atmospheric Lightening

9. Work of Scientists

10. Charles Augustin de Coulomb
1) Studied forces between the
two electrical Charges.
2) Established Coulomb’s Law.

11. Orested
Discovered that electric
current creates a
magnetic field.

12. Ampere
Discovered that an
electric current through
a coil acts like a
magnet.

13. Michael Faraday
Discovered electromagnetic
induction, the principle behind
the electric transformer and
generator.
Discovered how EMF
is induced in a coil when the
flux passing through the coil
changes.

14. James Clerk Maxwell
Discovered Theory of
electromagnetism, which
showed that light was
electromagnetic radiation
Electrical fields and magnetic
fields can couple together to
form electromagnetic waves.
Maxwell Equations

15. Heinrich Hertz
• Proved the existence of the
electromagnetic waves
predicted by James Clerk
Maxwell's equations of
electromagnetism.
• Proved that EM waves can
be polarized.

16. Marconi
Inventor of a successful
wireless telegraph (1896). In
1909 he received the Nobel
Prize for Physics

17. Electromagnetic Wave Propagation
• Ex = Eo sin(kz- t)
• By = Bo sin( kz- t)
• Propagation Vector
K = 2/
• Angular Frequency
= ck
• C = 1/ √(µoεo)
• Bo = Eo/C

18. • Velocity of Light in medium is C = 1/ √(µε)
• Velocity of Light depends on electric & magnetic
properties of medium.

19. General Properties of Electromagnetic Radiation
1)Electromagnetic waves are propagated by oscillating
electric fields and magnetic field oscillation at right angles to
each other.
2)These waves travel with speed 3×108ms−1 in vacuum.
3)They are not deflected by electric or magnetic field.
4)They can show interference or diffraction.
5)They are transverse waves.
6)May be polarized.
7)Need no medium of propagation.
8)wavelength and frequency related as c=ʋλ.

20. Electromagnetic Spectrum
Electromagnetic radiation has a wide spectrum, including
gamma rays, X-rays, UV rays, visible light, IR radiation,
microwaves, and radio waves.
The different colors of light differ in their frequencies (or
wavelengths).
Electromagnetic waves have an extremely wide range of
wavelengths, frequencies, and energies. The highest
energy form of electromagnetic waves are gamma (γ)
rays and the lowest energy form are radio waves.
The electromagnetic spectrum is a continuum of all
electromagnetic waves arranged according to frequency
and wavelength.

24. 1 PetaHertz (PHz) = 1015Hz
1Exahertz (EHz) = 1018 Hz
1 Terahertz(THz) = 1012 hertz.
1 Megahertz (MHz) = 106 hertz.
1kilo hertz (kHz) = 103 hertz.
1 gega hertz(GHz) = 109 hertz.

26. Production of X – Rays
Water inlet
Water outlet
F – Filament (Cathode)
T – Target ( Anode)
LT – Low tension Supply
HT – High tension Supply

27. Production of Electromagnetic Waves
Hert’z Experiment

28. Apparatus:-
1)High tension coil
2)Polished brass knobs
3)Metal Plates attached to spheres
4)Receiving loop

29. https://youtu.be/7b8VEhkKruw
High Voltage Source

30. https://youtu.be/FWCN_uI5ygY

31. Planck’s Hypothesis of Photon
All electromagnetic radiation is quantized & occurs
in finite bundles of energy called as photon.
The energy of photon , E = hʋ
Where,
h = 6.626x 10-34 Js
E = hc/