Frequency of Electromagnetic Waves
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This diagram looks at the frequency of electromagnetic waves.
- It shows that the frequency of electromagnetic radiation (light) refers to the number of wave-cycles of an electromagnetic wave that pass a given point in a given amount of time.
- The frequency of an electromagnetic wave can be thought about in the same way as the frequency of trains that pass through a railway station. If a train passes through a station every 10 minutes then the frequency is six trains per hour.
Remember that:
- The frequency of a wave should not be confused with the speed at which the wave travels or the distance it travels.
- The term frequency refers to the measurement of the frequency of wave oscillations that pass a given point in a given amount of time.
- The unit of measurement of frequency is the hertz. One hertz equals one wave-cycle per second.
- Because the frequency of some electromagnetic waves is so small, Hertz is sub-divided into kilohertz, megahertz, gigahertz and terahertz.
- The wavelength and frequency of light are closely related. In any given medium, the higher the frequency, the shorter the wavelength.
- The amount of energy transported by a light wave increases with the frequency of oscillations (wave-cycle) and as the length of each oscillation decreases.
Description
Frequency of Electromagnetic Waves
TRY SOME QUICK QUESTIONS AND ANSWERS TO GET STARTED
The hertz is used to measure the frequency of electromagnetic waves. Different prefixes denoting subdivisions are used to aid measurement eg. kilohertz (1,000 cycles/sec), megahertz ( 1,000,000 cycles/sec), gigahertz (1,000,000,000 cycles/sec) and terahertz (1,000,000,000,000 cycles/sec).
Violet has the highest frequency of visible light.
About the diagram
About the diagram
- This diagram looks at the frequency of electromagnetic waves.
- It shows that the frequency of electromagnetic radiation (light) refers to the number of wave-cycles of an electromagnetic wave that pass a given point in a given amount of time.
- The frequency of an electromagnetic wave can be thought about in the same way as the frequency of trains that pass through a railway station. If a train passes through a station every 10 minutes then the frequency is six trains per hour.
Remember that:
- The frequency of a wave should not be confused with the speed at which the wave travels or the distance it travels.
- The term frequency refers to the measurement of the frequency of wave oscillations that pass a given point in a given amount of time.
- The unit of measurement of frequency is the hertz. One hertz equals one wave-cycle per second.
- Because the frequency of some electromagnetic waves is so small, Hertz is sub-divided into kilohertz, megahertz, gigahertz and terahertz.
- The wavelength and frequency of light are closely related. In any given medium, the higher the frequency, the shorter the wavelength.
- The amount of energy transported by a light wave increases with the frequency of oscillations (wave-cycle) and as the length of each oscillation decreases.
Understanding the diagram:
- The diagram shows that the frequency of waves is counted in wave-cycles. One wave-cycle is shown as a dotted yellow line that follows the wave.
- The dotted yellow line below the wave measures three complete cycles. The measurement is from the peak of the first wave to the peak of the third.
- The point at which measurement of passing wave-cycles is taken is shown as a vertical line with a clock face below it.
- The measurement involves calculating how long it takes for the three wave-cycles to pass the clock.
- The diagram shows that the time it takes in this example is one second.
- The frequency, in this case, is 3 wave-cycles per second which equal 3 Hertz (Hz).
Some key terms
The hertz (symbol: Hz) is a unit used to measure the frequency of electromagnetic waves.
- Hertz are used when measuring the frequency of wave-cycles of electromagnetic waves.
- One hertz is defined as one cycle per second.
- Hertz measure the number of oscillations of the perpendicular electric and magnetic fields of electromagnetic radiation per second.
-
- 1 Hertz (Hz) = 1 cycle per second
- 1 Kilohertz (kHz) = 1,000 (thousand) cycles per second
- 1 Megahertz (MHz) = 1,000,000 (million) cycles per second
- 1 Gigahertz (GHz) = 1,000,000,000 (billion) cycles per second
- 1 Terahertz (THz) = 1,000,000,000,000 (trillion )cycles per second
Electromagnetic radiation refers to the transfer of all forms of radiation through space by electromagnetic waves.
- Electromagnetic radiation includes gamma rays, ultraviolet (UV), infrared (IR), X-rays, and radio waves, as well as visible light.
- Detached from its source, electromagnetic radiation (EM radiation), is transported by electromagnetic waves (or their quanta, photons) and propagates through empty space at the speed of light.
- Man-made technologies that produce electromagnetic radiation include radio and TV transmitters, radar, MRI scanners, microwave ovens, computer screens, mobile phones, all types of lights and lamps, electric blankets, electric bar heaters, lasers and x-ray machines.
A wave-cycle refers to the path of a wave measured from any point through the course of a single oscillation to the same point on the next oscillation.
- Imagine a wave-cycle as a series of points marked on the path of the wave between one crest and the next.
- All electromagnetic waves share features such as crests, troughs, oscillations, wavelength, frequency, amplitude, direction of travel.
- Whilst a wave-cycle is the path from one point on a wave during a single oscillation to the same point on completion of that oscillation, wavelength is a measurement of the same phenomenon along the axis of the wave.
An electromagnetic wave carries electromagnetic radiation.
- An electromagnetic wave is formed as electromagnetic radiation propagates from a light source, travels through space and encounters different materials.
- Electromagnetic waves can be imagined as synchronised oscillations of electric and magnetic fields that propagate at the speed of light in a vacuum.
- Electromagnetic waves are similar to other types of waves in so far as they can be measured in terms of wavelength, frequency and amplitude.
- We can feel electromagnetic waves release their energy when sunlight warms our skin.
- Remember that electromagnetic radiation can be described either as an oscillating wave or as a stream of particles, called photons, which also travel in a wave-like pattern.
- The notion of waves is often used to describe phenomena such as refraction or reflection whilst the particle analogy is used when dealing with phenomena such as diffraction and interference.
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