This presentation is about Propagation of Electromagnetic Waves and covers the following topics: -Introduction to EM Waves -Electromagnetic Wave Spectrum -Wave Propagation in Lossy Dielectrics -Plane Waves in Free Space -Properties of EM Waves This presentation is as per the course of DAE Electronics ELECT-212.

1. Electromagnetic
Wave Propagation
IRFAN SULTAN
INSTRUCTOR (TELECOM.)
GOVT. COLLEGE OF TECHNOLOGY

2. Contents
 Introduction to EM Waves.
 Electromagnetic Spectrum
 Wave Propagation in Lossy Dielectrics
 Plane Waves in Free Space
 Plane Waves in Good Conductors

3. Introduction to EM-Waves
 Electromagnetic Waves, also abbreviated as EM-Waves, are the waves
which consist of both Electric and Magnetic Fields and travel at a speed
same as that of light, i.e. 3x108 m/sec
 All forms of electromagnetic radiation consist of perpendicular oscillating
electric and magnetic fields.

4. Properties of EM-Waves
 Invisible
 Travel at speed of light
 Consist of Electric and Magnetic fields
 Electric Field, Magnetic Field and Direction of Propagation of an EM wave
are all perpendicular to each other
 Their Electric and Magnetic fields cannot be separated from each other
 The total energy of an EM wave is equally divided between Electric and
Magnetic fields
 When they pass through a metallic conductor they produce voltage across
the conductor

5. Properties of EM-Waves
 They don’t need any medium to travel
 Their intensity is same all around in free space
 When they travel from one place to another their power (intensity) is
reduced, i.e. they suffer from attenuation
 When they enter from one medium to another:
 Their form of energy changes, i.e. they suffer from Absorption
 They are diverted from their path, this process is called refraction
 When they pass through a hole they bent along sides when leaving the
hole, this process is called Deflection

6. Refraction, Absorption and Diffraction
Refraction
Reflection Diffraction
Absorption

7. Electromagnetic Spectrum
 EM Spectrum is the range of wavelengths or frequencies over which
electromagnetic radiation extends.
 It consists of different frequency bands which are basically groups of
certain frequency ranges.

8. Electromagnetic Spectrum

9. Waves
Longitudinal Waves Transverse Waves
Electromagnetic Waves
Electromagnetic Spectrum
Radiowave
Microwave
Infra-Red
Light
Ultra-Violet
X-ray
Gamma ray
Applications
Sound waves
Classified into
Comprises of

10. Some tips to help you to remember:
 EM Spectrum
Raja’s Mother Is Visiting Uncle Xavier’s Garden
 Visible Light Spectrum
Run Off You Girls Boys In View
Radio
wave
Micro
wave
Infra-red
Rays
Visible
light
Ultra-violet
ray
X-rays Gamma
rays
red orange yellow green blue indigo violet

11. Wave Propagation in Lossy Dielectrics
 A Lossy Dielectric is basically a medium which reduce the power of EM
waves, due to its “Poor Condition”, when they travel through it.
 In other words, a Lossy Dielectric is a practical conducting medium that is
neither a good conductor nor a good insulator.
 The following terms are used to describe the losses in a propagating wave:
 Attenuation Coefficient 𝛼
 Phase Coefficient 𝛽

12.  Attenuation Coefficient is measured in Neper Per Meter (Np/m) or Decibel
Per Meter (dB/m)
 1Np = 20log(e) = 8.686 dB
 Formulas for Velocity and Wavelength of a wave are:
Wave Propagation in Lossy Dielectrics
 Formulas for Attenuation and Phase coefficients are:
𝜎 = sigma = Conductivity
𝜇 = mu = Permeability
𝜔 = omega = Angular velocity
ε = epsilon = Permittivity

13. Plane Waves in Free Space
 This is a special case for which:
 Permeability 𝜇 = 𝜇𝑜 (Permeability of free space) = µ0 = 4π × 10−7 H
 Conductivity 𝜎 = 0
 Permittivity ε = εo (Permittivity of free space) = 8.85 x 10-12 F/m