radiowaves

• radio waves have the longest __________ and the lowest _________ of all the electromagnetic waves

  wavelength, frequency
• why do we call it the electromagnetic spectrum?

  because theyre made up of oscillating, electric and magnetic fields
• how can we generate electromagnetic waves?

  with electricity using an alternating current because alternating currents are made up of oscillating charges
• how do we generate radio waves?

  we use a device used to a transmitter that is connected to an oscilloscope.
• what does an oscilloscope show us ?

  the frequency of the alternating current on the screen
• why do we care about the frequency of the alternating current when using an oscilloscope to measure radio waves?


  its the alternating current that determines the frequency of the wave we are going to produce
• how does a receiver help us detect radio waves?

  it absorbs the energy and generates another alternating current that gets displayed on another oscilloscope
• the frequency on the oscilloscope connected to the receiver is the exact same as the _________ we used to generate the radio wave in the first place


  frequency
• what do radio waves allow us to do?

  transfer information
• what is the main use of radio waves?

  for communication
• what are the three types of radio waves?

  longwave, shortwave and very short wave
• what do long waves do?

  • transmitted huge distances (e.g. London to Singapore) without having to interact with anything along the way
  • this is because they diffract (bend) around the curved surface of the earth
  • they are great for long range communication
• what do short waves do?

  • they can also travel long distances
  • unable to curve around the earth
  • they are reflected from the ionosphere (an electrically charged layer of the upper atmosphere)
  • by bouncing back and forth between the ionosphere and earth repeatedly they can cover long distances
  • they can also work for short distances (like for connecting your phone to bluetooth)
• what do very short waves do?

  • used for tv and FM radio
  • they have to travel directly from your transmitter to your receiver
  • this is why you don't always get a good radio signal to your car. surroundings like hills and tunnels can get in the way of the direct transmission