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# F:\Electromagnetic Spectrum

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Presentation on the elctromagnetic spectrum prepared at Wilson´s Hospital School. Suitable for senior Physics.

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### F:\Electromagnetic Spectrum

1. 1. Electromagnetic spectrum <ul><li>The electromagnetic spectrum is more familiar to you than you might think. The microwave you use to heat your food and the cell phones you use are part of the Electromagnetic Spectrum. The light that our eyes can see is also part of the electromagnetic spectrum. This visible part of the electromagnetic spectrum consists of the colors that we see in a rainbow - from reds and oranges, through blues and purples. </li></ul><ul><li>Each of these colors actually corresponds to a different wavelength of light. </li></ul>
2. 2. What are electromagnetic waves? <ul><li>Electromagnetic waves are formed when an electric field (shown as blue arrows) couples with a magnetic field (shown as red arrows). The magnetic and electric fields of an electromagnetic wave are perpendicular to each other and to the direction of the wave. </li></ul>
3. 3. What speed do they move? <ul><li>Electromagnetic waves move at a speed of 299,792,458 metres per second (yes, you can round it up to 3 x 10 8 m/s. In other media, their speed is less </li></ul>
4. 4. Electromagnetic Waves have different wavelengths <ul><li>Radio waves, television waves, and microwaves are all types of electromagnetic waves. They differ from each other in wavelength. Wavelength is the distance between one wave crest to the next. </li></ul>
5. 5. <ul><li>EM waves are typically described by any of the following two physical properties: the frequency f and wavelength λ, </li></ul>The frequencies and wavelenghts of electromagnetic waves are related by the equation:
6. 6. Energy of electromagnetic waves All frequencies in the electromagnetic spectrum transmit energy at the speed of light . That’s why energy can be transferred by radiation (energy from the sun to the earth, the microwaves oven…)
7. 7. How to calculate energy for electromagnetic waves This energy is carried in smalll packs called photons . The energy per photon of an electromagnetic wave can be calculated from the Planck–Einstein equation : . where E is the energy, h is Planck's constant , and f is frequency h = 6.626 × 10 −34 joule-second
8. 8. How do the waves fit into the electromagnetic spectrum?
9. 10. Regions of the Electromagnetic Spectrum Listed below are the approximate wavelength, frequency, and energy limits of the various regions of the electromagnetic spectrum. > 2 x 10 -14 > 3 x 10 19 < 1 x 10 -11 Gamma-ray 2 x 10 -17 - 2 x 10 -14 3 x 10 16 - 3 x 10 19 1 x 10 -11 - 1 x 10 -8 X-ray 5 x 10 -19 - 2 x 10 -17 7.5 x 10 14 - 3 x 10 16 1 x 10 -8 - 4 x 10 -7 UV 3 x 10 -19 - 5 x 10 -19 4 x 10 14 - 7.5 x 10 14 4 x 10 -7 - 7 x 10 -7 Optical 2 x 10 -22 - 3 x 10 -19 3 x 10 11 - 4 x 10 14 7 x 10 -7 - 1 x 10 -3 Infrared 2 x 10 -24 - 2 x 10 -22 3 x 10 9 - 3 x 10 11 1 x 10 -3 - 1 x 10 -1 Microwave < 2 x 10 -24 < 3 x 10 9 > 1 x 10 -1 Radio Energy (J) Frequency (Hz) Wavelength (m)
10. 11. How do I remember all this?   meaning: R adio M icrowaves I nfra-Red V isible light U ltra-violet X -rays G amma rays   Try: R abbits M ate I n V ery U nusual e X pensive G ardens