12.1 - The nature of EM waves

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Mind Map by , created over 5 years ago

Physics HL (Option G - Electromagnetic Waves) Mind Map on 12.1 - The nature of EM waves, created by wondersnail on 03/07/2014.

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Created by wondersnail over 5 years ago
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12.1 - The nature of EM waves
1 G.1.1 - EM radiation
1.1 Radio waves - created by passing alternated current through a wire
1.2 Light wave - created from the electrons in an atom as they drop from high energy level to low
1.3 High-frequency waves (UV-light, x-rays, gamma-rays) - created by the nucleus of atoms
2 G.1.2 EM Spectrum
2.1 Radio waves - Alternating current in an electrical circuit
2.1.1 Frequency: 10^8 - 10^9
2.1.2 Used in communications
2.2 Microwaves - oscilliations of electrons in vacuum
2.2.1 Used in heating food due to microwaves having a frequency similar to that of water molcules
2.2.2 Frequency: 10^9 - 10^11
2.3 Infrared - energy released by atoms that give up heat
2.3.1 Frequency: 10^13 - 10^14
2.3.2 Used in TV remote controls, optical insutrments
2.4 Visible light - photons released by electrons de-exciting
2.4.1 Frequency: 10^15
2.4.2 Voilet: 380-450 nm
2.4.2.1 Blue: 450-495 nm
2.4.2.1.1 Green: 495-570 nm
2.4.2.1.1.1 Yellow: 570-590 nm
2.4.2.1.1.1.1 Orange: 590-620 nm
2.4.2.1.1.1.1.1 Red: 620-750 nm
3 G.1.3 - Dispersion
3.1 The angle of refraction is dependent on the wavelength of the radiation
3.1.1 This means that light of different wavelengths (coulours) does not bend equally much; as white light passes through a prism the blue light is bent more than the red light etc., and you will have a pretty rainbow!
4 G.1.5 - Physical properties of EM radiation
4.1 Transmission- when a wave does not have the correct frequency to interact with the atoms of a substance, the energy is sent away again, it is transmitted.
4.2 Absorption- when a wave does have the right frequency to interact with atoms of a substance, it gives energy to the electrons and excites them. The electrons has thus absorbed the energy.
4.3 Scattering- when a wave is forced to change direction due to small particles of e.g. water is in the way. The wave is sent off in a different direction, and is thus scattered.
5 G.1.7 - Lasers
5.1 Monochromatic light- light in which all photos have the same wavelength and therefore the same colour. This is why lasers always come in one colour only; the light is monochromatic
5.1.1
5.2 Coherent light- light in which all photons are released in the same direction and in phase. This is why lasers are beams of intense light and not, for example, a light bulb.
5.2.1 Both are needed in lasers!
5.2.1.1 Creating a laser
5.2.1.1.1 Population inversion is when a flash of light excites atoms, so there are more atoms withing the tube that are excited than are not. The atoms get de-excited, so they release photons in a random direction within the tube. When one of these photons pass by still excited photos they de-excite them too, in a sort of chain reaction that amplifies the light.
5.2.1.2 Uses of lasers
5.2.1.2.1 - Some fancy outlining of a use of lasers.

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