Electromagnetic Waves
Electromagnetic waves do not require a material medium for their propagation. They arise from the vibrations of electric (E) and magnetic (M) fields. The combination of these fields forms an Electromagnetic (E-M) wave.
The electric and magnetic fields in an electromagnetic wave are perpendicular to each other and to the direction of wave propagation. Examples include light waves, X-rays, and gamma rays.
Differences Between Electromagnetic and Mechanical Waves
- Electromagnetic waves travel at the speed of light, whereas mechanical waves travel at lower speeds.
- Mechanical waves can be transverse or longitudinal, but electromagnetic waves are always transverse.
Wavelength and Frequency
Like ocean waves, electromagnetic waves have peaks and troughs. The wavelength is the distance between two identical points on consecutive cycles of a wave, such as the distance between two peaks.
Electromagnetic radiation (EMR) can also be defined by its frequency, which is the number of wave crests passing a point per unit time. All EMR types travel at the speed of light, meaning the frequency depends on the wavelength: shorter wavelengths correspond to higher frequencies.
Credit: Freepik
Types of Radiation
Electromagnetic waves were first predicted by James Clerk Maxwell, who proposed that light is a form of electromagnetic radiation. Heinrich Hertz later provided experimental evidence of E-M waves.
Electromagnetic waves are classified by wavelength into the electromagnetic spectrum, which includes:
- Gamma rays
- X-rays
- Ultraviolet rays
- Visible light
- Infrared rays
- Microwaves
- Radio waves
Wave Properties
All electromagnetic waves share properties such as reflection, refraction, interference, and diffraction. However, they differ in wavelength, frequency, and interaction with matter.
The relationship between wavelength (λ) and frequency (f) is given by:
$$ λ = \frac{c}{f} $$ where c is the speed of light (3 × 108 m/s).
Applications of Electromagnetic Waves
- Radio Waves: Used in communication systems such as radios and televisions. Microwaves, a subset, are used in radar and cooking.
- Infrared Waves: Found in sunlight and electric lamps. Used in industrial drying, muscle treatment, and thermal imaging.
- Visible Light: Consists of the colors red, orange, yellow, green, blue, indigo, and violet. The Sun is the primary source of visible light.
- Ultraviolet Rays: Produced by the Sun and certain lamps. They can cause fluorescence and are used in sterilization.
- X-Rays: Generated by striking metal with fast-moving electrons. Used in medical imaging and industrial inspections.
- Gamma Rays: Emitted by radioactive substances. Used in cancer treatment and nuclear industry applications.
Detection of Electromagnetic Waves
- Gamma Rays: Geiger-Muller tube
- X-Rays: Photographic films
- Ultraviolet Rays: Photographic films, fluorescent substances
- Visible Light: Eye, photographic film, photoelectric cells
- Infrared Rays: Skin, thermometer, phototransistor, photographic film
- Radio Waves: Radio sets, television sets, aerials