Electromagnetic radiation (EMR) is a form of energy that flows in the form of electric or magnetic waves through a material medium or free space. EMR can take various forms such as microwaves, radio waves, gamma radiation, infrared light, ultraviolet light and so on. Electromagnetic waves travel at the speed of light through vacuum. EMR is produced whenever there is a change in the velocity of a charged particle.

Characteristics of electromagnetic radiation

  • Amplitude: This refers to the intensity or brightness of the EM waves. Amplitude is measured in meters.
  • Velocity: EM waves travel with the speed of light in vacuum, thus their velocity in vacuum is 300,000 kms per second. The velocity of electromagnetic waves slows down when they travel through a material. Velocity is a vector and thus has magnitude and direction.
  • Wavelength: Depending on the wavelength EMR can be of different types viz radio waves, microwaves and so on. As energy travels in waves, wavelength is the distance between two consecutive wave crests. Wavelength is denoted by the Greek alphabet Lambda ( λ ).

Wavelength | Image source: science.hq.nasa.gov

  • Frequency: The frequency of EMR is calculated as the velocity of the waves divided by the wavelength. Frequency is measured in Hertz. Frequency represents the number of times the wave repeats per second.

Did you know: The speed of light is always the same (equal to 2.99792458 x 108 m s-1)

Types of electromagnetic radiation
As discussed earlier, depending on the wavelength EMR can be of different types such as radio waves, microwaves, infrared, ultraviolet, X rays, Gamma rays and so on. Each of these have different uses. Let us take a look at the different types of electromagnetic radiation in detail.

Radio waves: The typical wavelength of radio waves could vary from 30 cms to 500 mts. Thus they cover a broad band of frequencies.They are used in communications for wireless transmission of sounds, and also for aircraft navigation. They are also used in remote sensing.

Microwaves: The typical wavelength of microwaves is around 15 cms. They are most commonly used in microwave ovens. Sometimes they are also used in Doppler radars.

Infrared: The typical wavelength is very small around 0.01 mm. We can not see infrared light but we can feel it due to its heat energy. This lies just beyond the red light in the light spectrum. One of the most common uses of shorter wavelength infrared waves is in the TV remote control.

Ultraviolet: The typical wavelength is 500 nanometers. This is a bluish light that lies beyond the highest frequency violet light that humans can see. Ultraviolet lamps are used in hospitals to sterilize and sanitize medical equipment. It is also used in the treatment of skin disorders and Vitamin D deficiency diseases as it is believed to help the body in producing Vitamin D.

X rays: The typical wavelength is 0.1 nanometers. X rays are very useful. They are used both in security scanning devices and medicine.

Gamma rays: The typical wavelength is 0.000001 nanometers. These are the most energetic and harmful form of electromagnetic waves. Gamma rays can be detected by their ability to ionize gas atoms or to create electron–hole pairs in substances that are semiconductors or insulators. Gamma rays are used for sanitizing medical supplies that cannot be sterilized by boiling in water.


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