• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Electromagnetic spectrum facts.

Extracts from this document...


Electromagnetic spectrum facts

  • Waves carry vibrations through a medium.
  • They transfer the energy locked up in the vibrations.
  • Waves have a measurable speed, wavelength and frequency.
  • Waves meeting a boundary between mediums may be reflected, refracted or absorbed - often a mixture of all three.
  • Waves passing through a gap may be diffracted (spread) - the spreading is only noticeable if the gap is similar to the wavelength.
  • Electromagnetic waves carry transverse vibrations in electrical and magnetic fields, not vibrating particles.
  • E-m waves don't need matter to travel through - they can travel through empty space (a vacuum).
  • In a vacuum, all e-m waves travel at (approximately) 300 million metres per second (3 x 108m/s) - the fastest speed in the universe.
  • When e-m waves travel through matter (for example, light through air or glass), they travel a bit slower than this but rarely less than half as fast as in vacuum.
  • Waves of different frequencies travel at different speeds in transparent matter - so a mixture of waves can be separated out by diffraction. For example, white light is split up into a mixture of colours when it goes through a prism.
...read more.


Check your syllabus to see if there are particular examples or applications you need to know about in detail. This summary should give you some useful background ideas and information.

Why a spectrum?

At first sight, these waves seem a pretty mixed bunch. However:

  • they can all travel in a vacuum without a material medium (stuff) to carry the vibrations
  • they all have the same enormous speed in a vacuum; (3 x 108m/s)
  • they all have a similarity in their sources - all involve electrical charges accelerating or vibrating (not obvious, not easy, and not normally examined in GCSE - but very important!)

Notice that as the waves get shorter the dangers of over-exposure get more drastic, even for quite weak sources. The shorter the waves, the more drastic the effect on atoms that absorb them.

  • Long wave - particles (molecules) wobble, matter gets hotter
  • Short waves - particles split up and/or ionise (form charged particles), heating and chemical changes

Hence the greater precautions taken with short waves:

  • ultraviolet - skin blockers, sunglasses
  • X-rays,gamma-rays - lead shields, minimal exposure, keeping away


...read more.


The frequency (f) is the number of complete waves passing a point each second. It's a 'number per second' so it's measured in /s or s-1; usually called hertz (Hz) after a German physicist.

1 kilohertz = 1 kHz = 1000 Hz
1 megahertz = 1 MHz = 1,000,000 Hz
For example:
100 complete sound waves enter your ear in a second (you'd hear a deep hum).
f = 100 per second
= 100 /s = 100 s
= 100Hz

The speed of a wave (v) is just what it says. It's the speed at which the vibrations in the wave move from one point to the next. Wave speed is measured in metres per second (m/s, ms-1).

For example:
speed of sound in air = 330 m/s (approximate)
speed of light in space = 300,000,000 m/s

Print out or copy this page if you want a basic revision sheet. You may want to check out the next section first.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Waves & Cosmology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Waves & Cosmology essays

  1. Experiment B11: Measuring focal length of lenses

    Moreover, it may be too difficult for students to adjust the apparatus to the right place and get the required value. Therefore method (a): "Object & image distance method" is a fast accurate and easy method to measure the focal length of the convex lens.

  2. Investigate any relationship present between the distance between a solar cell and a lamp, ...

    1 1 1 95 1 1 1 1 100 1 1 1 1 On this table are the results of the first experiment. In this experiment, I varied the power supplied to the lamp to see the output to the solar cell.

  1. investigate how and why the depth of water affects wave speed

    When three refraction's have taken place I will stop the stopwatch and record the time. I will then repeat this three times, and then move on to a depth of 2cm, then 3cm, then 4cm, 5cm and finally 6cm. These tests will also be repeated 3 times and averaged.

  2. Free essay

    OCR Physics B Research Project - The Expanding Universe

    v = H0d d = v/H0 = (1.5x108/1000)/75 = 2000Mpc (using H0 = 75 kms-1Mpc-1) One Mpc is roughly 3.26x106 light years, so the star would be about 6.5 billion light years distant. Fred Zwicky suggested in 1929 that light may lose energy as it travels, which would explain the proportional relationship between red shift and distance.

  1. Is Space Exploration Worth the Cost?

    and other information about Earth and all the many things that exist around it. Satellites are used in weather reports, television transmission, everyday telephone calls, GPS and scientific research. The main function of satellites is to receive and send signals all across the globe.

  2. Velocity of a wave in a tank at varying depths of water

    Were the investigation to be repeated, more results would be gathered from a greater range of depths in order to get a more accurate line of best fit and further lower the impact that the random error had on this investigation.

  1. Estimating the wavelength of light using a double-slit and a plane diffraction grating

    Green(1st order)(2) Green(2nd order) x/m 0.17 0.16 0.354 tan? 0.17 0.16 0.354 sin? 0.168 0.158 0.334 ?=dsin?/m 5.58x10-7 5.26x10-7 5.56x10-7 Colour Red(1st order) Red(1st order)(2) Red(2nd order) x/m 0.214 0.203 0.45 tan? 0.214 0.203 0.45 sin? 0.209 0.199 0.410 ?=dsin?/m 6.97x10-7 6.62x10-7 6.83x10-7 4. Comment on your results. What are the major sources of error?

  2. Waves and Cosmology - AQA GCE Physics Revision Notes

    * The beta particles emitted in beta decay have a range of energies from virtually 0 to maximum energy. In beta decay, Etotal of recoil nucleus and ? particle are not always constant ? leading to a suggestion that a ? particle is not the only particle emitted during beta

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work