Electromagnetic Waves

Electromagnetic waves are synchronised oscillations of magnetic and electric fields, at right angles to the direction of wave travel.

Diagram illustrating electromagnetic waves with interlinked red and blue curved lines. The blue line represents the electric field, marked with a symbol (E), and the red line represents the magnetic field, marked with a symbol (B). Both fields are perpendicular to each other. The distance between two peaks of the blue wave is labelled as 'wavelength', marked with the symbol (λ). The waves travel in a direction indicated by an arrow.

Electromagnetic waves transfer energy from the source of the waves to an absorber. For example, in a toaster, infrared radiation comes from the grill/heating element and heats the toast. So, infrared carries energy from the heating element to the toast.

Properties of Electromagnetic waves

All electromagnetic waves share the following properties:

  • They are transverse waves – This means they oscillate perpendicular to the direction of energy transfer.
  • They can travel through a vacuum (such as space) – This is because they don’t need a material or substance to move through.
  • They travel at the same speed through air or a vacuum (empty space) – Electromagnetic waves travel at a speed of 300,000,000 metres per second (m/s) through a vacuum

The Electromagnetic Spectrum

Electromagnetic waves form a continuous spectrum called the electromagnetic spectrum.

The waves in the electromagnetic spectrum are arranged in order, from the longest wavelength (lowest frequency) to the shortest wavelength (highest frequency).

Illustrative chart depicting the electromagnetic spectrum, ranging from radio waves to gamma rays. At the top, each type of wave is paired with its source: FM TV for Radio, Microwave Oven for Microwaves, TV Remote for Infrared, Light Bulb for Visible Light, Sun for Ultraviolet, X-ray Machine for X-rays, and Radioactive Elements for Gamma. Beneath, colourful waveforms represent each type, with radio waves being the longest and gamma rays being the tightest. The middle section indicates increasing wavelength in metres, and the bottom shows comparative sizes of wavelengths, from buildings for radio waves to subatomic particles for gamma rays, alongside increasing frequency in Hertz.

As you go from left to right on the electromagnetic spectrum, there is a decrease in wavelength and an increase in frequency. Therefore, radio waves have the longest wavelength and lowest frequency. In contrast, gamma rays have the shortest wavelength and the highest frequency.

  • There is an inverse relationship between frequency and wavelength; as one goes up, the other goes down.

There are seven types of electromagnetic waves:

1. Radio waves

2. Microwaves

3. Infrared

4. Visible light

5. Ultraviolet

6. X-rays

7. Gamma rays

The human eye can only detect a limited range of frequencies, which we call visible light. However, we can use specific instruments to detect other waves in the electromagnetic spectrum.

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