Lecture on Electromagnetic Waves

Introduction

• Electromagnetic waves are both electric and magnetic in nature.
• Produced when a charge changes direction or speed.
• Electromagnetic waves consist of perpendicular electric and magnetic fields.

Production and Transmission

• Electric current in a wire creates a magnetic field.
• A solenoid (coiled wire) with current acts as a magnet; with iron core, it's an electromagnet.
• Electromagnetic waves are transverse waves.
• Travel in a vacuum at speed of light (3 x 10^8 m/s).

Properties of Electromagnetic Waves

1. Produced by accelerated/oscillating charges.
2. Do not require a medium for propagation.
3. Travel at speed of light in free space.

Historical Development

• James Clerk Maxwell: Developed electromagnetic wave theory, proving light as an electromagnetic wave.
• Heinrich Hertz: Proved existence of radio waves.
• Michael Faraday: Discovered electromagnetic induction.
• André-Marie Ampère: Formulated Ampère's Law.
• Hans Christian Ørsted: Discovered magnetic effect of electric current.

Electromagnetic Spectrum

• Arranged by frequency and wavelength.
• Inversely proportional relationship between wavelength and frequency.
• Spectrum includes: Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

Characteristics of Waves

• Amplitude: Maximum field strength.
• Frequency: Waves per second (measured in Hertz).
• Wavelength: Length of a wave (measured in meters).
• Speed of wave (V) = Wavelength (λ) x Frequency (f).

Sample Problem

• Calculate frequency of radio waves with 20m wavelength.
  • Given: Speed of light = 3 x 10^8 m/s.
  • Frequency = Speed / Wavelength = 1.5 x 10^7 Hz.

Conclusion

• Electromagnetic waves transfer energy.
• All travel at the same speed in a vacuum.
• Stay tuned for practical applications in the next session.