Electromagnetic waves

Electromagnetic waves

1. Electromagnetic Spectrum

   • Electromagnetic waves-Coexist as electrical and magnetic disturbances
     • Electrical waves+Magnetic waves=Electromagnetic waves
   • Light is another word for electromagnetic waves.
   • Electromagnetic waves(E.M.waves) travel at a constant speed in a vacuum
     • They travel slower through any other medium
       • This is because it's affected by a magnetic field,proving light has some electrical properties
     • Velocity of light through space/in a vacuum is 3x10^8 m/s
       • ^ means to the power of
       • Velocity-measurement of speed of something moving in a particular direction
   • The amount of energy an electromagnetic wave is carrying depends on 2 things:amplitude and frequency
     • Amount of energy carried in any wave depends on 1 thing:amplitude
   • The bigger the amplitude,the larger the amount of energy any wave is carrying
   • Gamma rays(Viewing internal organs),astronomy
     • X-rays(Viewing internal organs)
       • Ultraviolet waves(tanning beds)
         • Visible waves(sunlight,light bulb)
           • Infrared waves(remote control,heating)
             • Microwaves-(heating food,carrying phone signals)
               • Radio waves(carry radio+TV signals)
                 • Low Frequency.<400nm
           • This list is the Electromagnetic Spectrum
           • Only E.M.wave visible to human eye
     • High frequency(as you move down the list,frequency gets loweri.e.high-low).>700nm
   • Sound measured as 'loudness'
   • Frequency sensed as visible light of colour
   • Higher the frequency of an electromagnetic wave,larger the energy it 's carrying
   • When frequency changes wavelength changes

2. Light,infrared,microwaves and radio waves

   • Infrared is called infrared as 'infra' means below so it means 'below red'.The frequency of infrared radiation is lower than the frequency of red light.UV is after violet on the visible light spectrum meaning the frequency of UV radiation is higher than the frequency of violet light
     • Visible light spectrum:Red,Orange,Yellow,Green,Blue,Indigo,Violet
   • White light contains all the colours of the visible light spectrum
   • Infrared radiation used to carry signals from remote controls+inside optical fibers
     • Microwaves used to carry satellite TV programmes+phone calls(phone radiation at near-microwave frequencies)
       • Radio waves used for radio+TV broadcasting,radio communications+phone calls
   • Different types of EM wave radiation are hazardous in different ways.Microwaves+radio waves can heat the internal organs.Infrared radiation can cause skin burns
   • When all the colours have been absorbed the colour is white.When they've all been reflected the colour is black.To get a specific colour,all the colours of the visible light spectrum are absorbed apart from the specific colour

3. Radiation from ionising EM waves

   • Higher the Hz of EM waves the more energy they carry
   • Gamma rays are used for sterilisation as they're able to kill bacteria due to gamma rays having lots of energy as they have a high frequency
   • UV light can ionise skin cells damaging living cells such as your skin but the amount of damage depends on how long and how much of the rays you're exposed to
   • When X-rays hit the special film,they darken the region.Bones absorb X-rays and the region on the film just behind the bones stay undarkened
   • Ionisation-process of making an atom ion(when going through a substance can knock electrons out of atom.Atoms become charged as lost electrons).Damaging cells and tissues.
   • Gamma rays(γ-also means gamma rays),X-rays and UV rays are ionising.Damage body's cells and tissues.Can destroy tumors
   • Radiation-process of emitting some energy
   • Ionised atoms behave differently than neutral atoms in a chemical reaction.This may undermine health
   • Radiation dose-depends on how much energy in transfers per second and the type of radiation
     • Part of your body receives the energy

4. EM waves

   • Can be reflected and refracted
     • When travelling between 2 different mediums,the wave speed and wavelength change and they're also directly proportional i.e. if wave speed halves wavelength halves,if wave speed doubles wavelength doubles.The frequency doesn't change due to the no.of oscillations staying the same even when the wave speed and wavelength change. Since wave speed changes when travelling between 2 different mediums, when a wave crosses to a new medium at an angle(excluding 90 degrees) the change of wave speed causes the wave's motion to change direction, making it look like it's bending
   • Carry energy
   • Higher the frequency of the EM wave,more energy it carries
     • higher the frequency, the lower the wavelength
   • Speed of all EM waves is constant (use letter c to represent constant)in a vacuum
     • speed of light in vacuum=3x10^8m/s
     • Speed of light travels slower in any other medium
   • Hotter the object,more infrared it emits(gives off)
     • Everything that has a temperature emits infrared radiation
   • When a wave hits an object(incident wave which is a wave that hits an object)some of it is reflected(reflected wave),some of it goes through the material(transmission,which can also result in refraction)and some of its energy is absorbed(absorption)
   • Dark,dull,rough surfaces coloured objects emit more infrared waves than light,shiny colouredobjects at the same temperature
     • Objects that are good at emitting are also good at absorbing
       • Dark and rough surfaced objects absorb infrared waves better than light shiny-surfaced objects

5. Reflected light

   • All light reflects off a boundary that is between 2 mediums of probagation(probagation meaning to go through)
   • Law of reflection
     • For every reflection,the incidence ray is equal to the reflected ray

6. Communications

   • The microphone converts the sound wave into electric currents
     • The oscillator produces an alternating(a current that constantly reverses its direction)electric current called a carrier wave(which is the audio signal)
       • The carrier wave and electric current are travelling in different cables and the transmittor combines the electric current of the sound wave with the carrier wave
         • The electrons in the metal oscillates up and down changing amplitude and frequency. The frequencies and amplitudes of the oscillating electrons replicates(matches up) the frequencies and amplitudes of the electric currents of the sound waves from the microphone
           • Radio waves are then produced from the different frequencie and amplitudes of the vibrating electrons
             • The receiver accepts the radio waves
               • The speaker then produces sound waves i.e.sound
   • Carrier waves are used to carry information and signals.They do this by varying(fluctuating/changing)their amplitude

7. THE SPEED OF ELECTROMAGNETIC WAVES IN AIR=300 MILLION M/S

Images and files in the map