Electromagnetic Waves - Engineering Physics - CSE 2026 - Shoolini University

2. Electromagnetic Waves

What do you mean by Electromagnetic Waves? What are the advantages of Electromagnetic Waves?

Electromagnetic Waves (EM Waves)

We studied Energy, a measure of the ability to do work, comes in many forms and can transform from one type to another. An example of stored or potential energy include batteries and water behind a dam and Objects in motion are examples of kinetic energy. Charged particles—such as electrons and protons—create electromagnetic fields when they move, and these fields transport the type of energy which we call an electromagnetic radiation, or light. Electromagnetic radiations are composed of electromagnetic waves that are produced when an electric field comes in contact with the magnetic field. A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. Electromagnetic waves were first postulated by James Clerk Maxwell and subsequently confirmed by Heinrich Hertz. Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz. Electromagnetic waves are created as a result of vibrations between an electric and a magnetic field. It can also be said that electromagnetic waves are the composition of oscillating electric and magnetic fields. Electromagnetic waves are solutions of Maxwell's equations, which are the fundamental equations of electrodynamics.

How EM waves are formed.

Electromagnetic waves are formed when an electric field comes in contact with a magnetic field. They are hence known as 'electromagnetic' waves. The electric field and magnetic field of an electromagnetic wave are perpendicular (at right angles) to each other.

Technological Applications of Electromagnetic Waves

Ever wonder how your mobile phone can carry your voice to someone else across the world? It does so by using electromagnetic waves. These are fluctuations in magnetic and electric fields that can travel through space. Since they have no tether to physical material, they can pass through walls, buildings, and even our bodies. Electromagnetic waves play a massive role in our lives. We can enjoy mobile phones, radio, TV, and more by controlling and manipulating these waves. Light testing equipment also checks for the presence of EM waves. So, EM waves are much more relevant than we might think. Delve into some of the technological applications of electromagnetic waves and discover how they’ve been making our lives easier for decades.

Radio Waves

First, we'll examine the most common application of EM waves—radio waves. A radio wave can broadcast FM and AM radio signals, but it can also do more. Your television uses radio waves to broadcast the signal from various TV stations (assuming you're watching analog TV instead of streaming). Finally, radio waves have applications in the military through radar. That's why radar and radio begin with the same three letters.

Microwaves

Another form of an EM wave is a microwave. As you probably guessed, these are the waves that a household microwave uses to heat food. That's not their only use, though. Microwaves are pretty similar to radio waves as they're also used for communication. TV stations use microwaves to send their signals out to longer distances.

Infrared Waves

An infrared wave generates heat, and it's also used in TV remote controls. In today's age, Bluetooth technology has primarily replaced infrared. Yet, infrared waves are necessary for creating heat-vision and night-vision cameras. That's because every living creature emits heat, which is infrared waves. That means anything that gets hot is producing a lot of infrared waves.

X- Rays

An x-ray is simply a form of EM wave used for internal photography. It uses a penetrating form of EM radiation to take pictures inside your body. The medical field uses the same EM radiation type as a cancer treatment. The radiation is concentrated in a high-energy form to eliminate cancer cells.

Characterstics of EM Waves

  1. Field of Electromagnetic wave

    There are two fields of the electromagnetic waves

    1. Electric Field
    2. Magnetic Field
  2. Field Angle of Electromagnetic Wave

    In the electromagnetic waves, the angle between the electric field and magnetic field is 90 degree or magnetic and electric fields are perpendicular to each other.

  3. Direction Of Electromagnetic Wave During Propagation

    The electric field and magnetic field is perpendicular to the direction of propagation

  4. Reflection of Electromagnetic Waves

    The Electromagnetic wave is having the characteristics of reflection just like the light waves. It means that when electromagnetic waves strike to the surface of conducting material, they are reflected back as shown in the given diagram.

  5. Refraction of Electromagnetic Waves

    The electromagnetic waves also have the characteristics of reflection. It means that when the electromagnetic waves inters from one medium to another, it bends towards the normal or away from the normal while traveling in the next medium. When the electromagnetic waves inter form rare medium to dens medium, it bends towards the normal and when the electromagnetic inter from dens to rare medium it bends away from the normal.

  6. Intensity of Electromagnetic Waves

    The intensity of electromagnetic waves depends on the electrical field strength of the wave. It means that if the field strength of electromagnetic waves is more, its intensity will be more and vice versa.
    The electrical field strength is measured in V/m volt per meter. For the microwave it's measured in micro volt per meter µv/m.

  7. Attenuation of Electromagnetic Waves

    When the electromagnetic wave is propagated its energy is wasted while travelling from source to load. This loss of energy is known as attenuation of the electromagnetic waves. The attenuation occurs due to buildings, tree's, hills, rivers etc. which observe the electromagnetic energy during propagation.

  8. Polarization of Electromagnetic Waves

    There are the following types of electromagnetic waves polarization.

    1. Vertical Polarization

      If the position of the electric field is vertical with respect to ground during propagation, it is called vertical polarization of electromagnetic waves.

    2. Horizontal Polarization

      If the position of the electric field is horizontal with respect to ground during propagation, it is called horizontal polarization of the electromagnetic waves.

    3. Linear polarization

      If the position of electric field is sometimes vertical and sometimes horizontal with equal intervals and the direction of propagation does not change, it is called linear polarization.

    4. Circular Polarization

      If the position of electric field changes continuously during propagation of electromagnetic waves and its intensity remains the same, its is called circular polarization.

    5. Elliptical polarization

      If the position and intensity of electrical field changes continuously during propagation, it is called elliptical polarization.

  9. Field Position of Electromagnetic Waves

    As we know that the electrical field and magnetic field are perpendicular to each other and at the same time these fields are perpendicular to the direction of propagation, if we change the direction of any field it well result in corresponding change of the other field. It means that if E-field is vertical, the H-field will be horizontal. Now if we change the position of the E-field from vertical to horizontal, the position of H0field (magnetic field) will also change from horizontal to vertical. If we change the direction of E-field or H-field the direction of propagation will also change if we change the direction of E0field and H-field at the same time the direction of propagation will remain the same.

  10. Velocity of Electromagnetic Waves

    Velocity of electromagnetic waves in the air is the same as the velocity of light. It is 3 X 108 m/s or 3 X 1010 cm/s.

  11. Separation of fields of EM Wave

    Electrical field and magnetic are always related to each other and whenever there is electric field, the magnetic field will also be present over there.

  12. Energy of EM Waves

    When the electromagnetic waves are propagated, the energy of these waves is equally distributed in electric field and magnetic field throughout the propagation.

Polarization

Polarization is a measurement of the electromagnetic field's alignment. In the figure above, the electric field (in red) is vertically polarized. Think of a throwing a Frisbee at a picket fence. In one orientation it will pass through, in another it will be rejected. This is similar to how sunglasses are able to eliminate glare by absorbing the polarized portion of the light.

Frequency

The number of crests that pass a given point within one second is described as the frequency of the wave. One wave—or cycle—per second is called a Hertz (Hz), after Heinrich Hertz who established the existence of radio waves. A wave with two cycles that pass a point in one second has a frequency of 2 Hz.

Wavelength

Electromagnetic waves have crests and troughs similar to those of ocean waves. The distance between crests is the wavelength. The shortest wavelengths are just fractions of the size of an atom, while the longest wavelengths scientists currently study can be larger than the diameter of our planet! More of that in Electromagnetic Spectrum.

Additional Reading:

  1. Maxwell Field Equations
  2. Time Variation
  3. Wave Equation
  4. Characterstics of EM Wave Propagation
  5. Energy integral - Power Flow anf Poynting Vector
  6. Snell's Law
  7. Signal Distortion
  8. Ground Wave Propagation
  9. Attenuation
  10. VLF / ELF Wave Propagation
  11. Tropospheric Super Refraction and Scattering
  12. EM Waves in Magnetoionic Medium - Appleton-Hartree Formula
  13. Ray Theory
  14. Equatorial Ionosphere Anomaly
  15. Electron Density Profiling
  16. Conductivities and currents in D-region and E-region
  17. Middle Atmospheric Dynamics
  18. Whistler Propagation
  19. Planetary Molecular Absorptions