electromagnetic spectrum

• all EM waves are ... waves

  transverse
• EM waves travel at the ... speed


  same
• at what speed do EM waves travel at?

  300,000,000 m/s (speed of light)
• do EM waves require a medium to travel through?


  no
• EM waves form a continuous spectrum over a range of...

  frequencies
• why is there a large range of frequencies across the EM spectrum?

  because they are generated by a variety of changed in their atoms and their nuclei (e.g. changes in the nucleus of an atom creates gamma rays)
• because of their different properties, EM waves are...


  used for different purposes
• waves on the electromagnetic spectrum in order

  radio waves, microwaves, infrared, visible light, ultraviolet, x-rays and gamma rays
• electromagnetic spectrum diagram

  
• waves lower down on the EM spectrum have ... wavelengths


  bigger
• waves higher up on the EM spectrum have ... wavelengths


  smaller
• radio wave wavelength


  1m - 10⁴m
• microwave wavelength


  10⁻²m
• infrared wavelength


  10⁻⁵m
• visible light wavelength


  10⁻⁷m
• ultraviolet wavelength


  10⁻⁸m
• x-rays wavelength


  10⁻¹⁰m
• gamma rays wavelength


  10⁻¹⁵m
• radio waves are made up of...

  oscillating electric and magnetic fields
• the frequency of the waves produced will be equal to...

  the frequency of the alternating current
• alternating current


  made up of oscillating charges - as the charges oscillate, they produce oscillating electric and magnetic fields, i.e. electromagnetic waves
• transmitter


  a device that sends out signals in the form of radio waves
• receiver


  a device which absorbs radio waves from a transmitter
• radio waves are used mainly for...

  communication
• long-wave radio waves can be transmitted and received from...

  halfway round the world
• how can radio waves travel so far?


  because they diffract (bend) around the curved surface of the Earth, even around hills and into tunnels
• short-wave radio waves can be transmitted and received from...

  long distances, because they are reflected from the ionosphere (an electrically charged layer in the Earth's upper atmosphere)
• how does Bluetooth use radio waves?

  Bluetooth uses short-wave radio waves to send data over short distances between devices without wires
• radio waves used for ... transmission have very short wavelengths

  TV and FM radio
• microwaves are used by...

  satellites
• how are microwaves used in microwaves?


  the microwaves are absorbed by the water molecules in the food and transfer energy into them and thus heating and cooking the food
• infrared radiation can be used to...

  monitor temperature
• infrared radiation is given out by...

  all objects. the hotter the object, the more infrared radiation it gives out
• how does infrared radiation monitor temperature?

  the infrared camera detects infrared radiation and turns it into an electrical signal, which is displayed on a screen. the over an objects the brighter it appears
• fibre optic cables use ... to transmit data

  visible light
• optical fibres


  thin glass or plastic fibres that carry data (e.g. from telephones) over long distances as pulses of visible light. work by reflection
• visible light spectrum


  red, orange, yellow, green, blue, indigo, violet
• ultraviolet radiation gives...


  skin a tan
• fluorescence


  the property of a mineral in which the mineral glows under ultraviolet light
• fluorescent lights generate ...

  UV radiation, which is absorbed and re-emitted as visible light by a layer of a compound called phosphor on the inside of a bulb