• 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...

Introduction

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.

Middle

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

image01.png

...read more.

Conclusion

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
-1
= 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. Peer reviewed

    Properties of Waves.

    3 star(s)

    Normal: An imaginary line at a right angle to the surface. Incident ray: The ray of light from the light source to the mirror. Reflected ray: The ray of light that has been reflected off the mirror. Angle of reflection (r): The angle between the normal and the reflected ray.

  2. Experiment B11: Measuring focal length of lenses

    The percentage error of the measured value obtained by method (c) is 8%, and the one obtained by method (d) is 19.109%. When compare the percentage errors, the percentage error of the measured value obtained by method (c) is more accurate than the other one.

  1. Is Space Exploration Worth the Cost?

    The key components are antennas, receivers and transmitters. Most satellites use both power from the Sun and batteries to work. They catch the Sun's energy using solar panels that point at the sun.

  2. Making sense of data - finding a value for the young modulus of a ...

    Hence I adopted this method. Analysis Results - Preliminary Before we went onto the main experiment, we spent out first lesson conducting a preliminary experiment to get a feel of how everything works.

  1. Diffraction Grating with White Light Source

    Apart from this, the white used in the experiment contains the visible light which has a composition of different wavelength of light.

  2. Investigating the relation between wave speed and tension in a slinky spring

    This way nobody can step on or trip over the apparatus. * Take special care with the slinky spring as it can be damaged by pulling it wide apart and then letting go. Fair Test To make this a fair test I will make sure that I will use the

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

    Using a plane diffraction grating 3. Tabulate the results: For a grating of 3000 lines per cm, Grating separation d=(1/3000) cm=3.33x10 Colour Blue(1st order) Blue(1st order)(2) Blue(2nd order) x/m 0.155 0.15 0.314 tan? 0.155 0.15 0.314 sin? 0.153 0.148 0.300 ?=dsin?/m 5.09x10-7 4.93x10-7 4.995x10-7 Colour Green(1st order) Green(1st order)(2) Green(2nd order) x/m 0.17 0.16 0.354 tan?

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

    Firstly I will measure exactly the depth of water that I need and make sure that I do not even go over or under by 1mm. Next, I need to keep a steady eye on the waves as they can travel quite fast and can sometimes be confusing as they get smaller.

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