1. Electromagnetic Radiation

2. Electromagnetic spectrum

3. “Let there be electricity an magnetism and there is light”
J.C. Maxwell
Maxwell’s equations are independent of wavelength

4. For stationary charges
Coulomb’s law
the electric force field
© 2005 Pearson Prentice Hall, Inc

5. © 2005 Pearson Prentice Hall, Inc

6. If a charge moves nonuniformly, it radiates
© 2005 Pearson Prentice Hall, Inc
If a charge moves nonuniformly, it radiates

7. The electric field of a moving point charge

8. Electric field
:unit vector directed from q to P at earlier time q - P

9. The retarded time/ the time delay
The retarded distance = r

10. Law of radiation

11. Magnetic field

12. Electric field produced by a slowly moving charge q at a distance r
©SB/SPK

13. Sinusoidal OscillationP
©SB/SPK

14. Electric field

15. Electric field along x axis

16. Electric field at a large distance

17. Magnetic field

18. ELECTROMAGNETIC WAVE is a TRANSVERSE WAVE

19. e0 : permitivity of free space
m0: permeability of free space
Maxwell’s wave equation in free space

20. Dipole moment
Charge q oscillating as y(t) produces the
same electric field as q/2 moving as y(t)
and –q/2 moving as –y(t)
The latter is an oscillating dipole

21. Electric field in terms of dipole moment

22. Current

23. Electric field in terms of current

24. Electric field at a distance r at time t

25. Energy Density: Energy per unit volume

26. Average Energy Density

27. Energy Flux Density: Energy per unit area
per unit time

28. Power radiated per unit solid angle

29. Radiation pattern of electric dipole

30. Electric Dipole Oscillator
© SPK/SB

31. Dipole radiation
© SPK/SB

32. © SPK/SB

33. Car Antenna
TV Antenna

34. Ooty Radio Telescope 0.5 m 530 m long 30 m wide parabolic cylinder
1054 dipoles, MHz
© SB

35. 0.5 m
© SB

36. The Radio Milky Way
The image shows the Milky Way galaxy as it would appear if we could see the electromagnetic energy the hydrogen in the galaxy emits in the Radio region, specifically the 21-cm wavelength. This image is computer generated from data collected by various radio telescopes.
© NRAO Green Bank

37. Microwave background fluctuation
cosmic microwave background fluctuations are extremely faint. The cosmic microwave background radiation is a remnant of the Big Bang and the fluctuations are the imprint of density contrast in the early universe.

38. Ultraviolet Galaxy NGC 1365
©NASA/JPL-Caltech/SSC

39. Summary Accelerating charge gives rise to radiation
Sinusoidal motion of charge gives rise to electromagnetic
radiation gives rise to plane electromagnetic wave at a
large distance.
The direction of electric field, magnetic field and propagation
are mutually perpendicular to each other.
Electric and magnetic field are in phase.

40. Images from Astra's Stellar Cartography Demo
Reference
1. FEYNMAN LECTURES ON PHYSICS VOL I
Author : RICHARD P FEYNMAN,
IIT KGP Central Library
Class no.  530.4
2. OPTICS
Author: EUGENE HECHT
Class no. 535/Hec/O
Images from Astra's Stellar Cartography Demo