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Electromagnetic Waves

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Presentation on theme: "Electromagnetic Waves"— Presentation transcript:

1 Electromagnetic Waves
these are made by vibrating electrical charges that can travel through space where matter is not present They do NOT require matter to move through      

2 Properties of Electromagnetic Waves
1.  All matter contains charged particles that are always in motion 2.  As a result, all objects emit electromagnetic waves Think about this:  Electromagnetic waves from the sun cause electrons in your skin to vibrate and gain energy 3.  The energy carries by an electromagnetic wave is called  RADIANT ENERGY                           Radiant energy feels warm!

3 Electromagnetic Waves
Have a speed - because light is an EM wave, the speed of these waves in space is referred to as "speed of light" The speed of light is nature's speed limit - as far as we know, nothing can travel faster than light. If space travel is every going to take us anywhere, we need to find a way to travel long distances quickly.


5 Electromagnetic Waves also have a frequency and a wavelength:
Wavelength = the distance between the crest of one wave and the next crest Frequency = the number of waves that pass a point in 1 sec

6 Waves & Particles Wave = a disturbance that carries energy Particles =
              a piece of matter When electromagnetic waves behave as particles, they are called PHOTONS

7 The Electromagnetic Spectrum
Waves have a variety of frequencies which determine how much energy they carry. The part of the spectrum we can see with our eyes is called   VISIBLE LIGHT

8 Radio Waves Right now, all around you are radio waves.  Even if you look closely you still can't see them.  If you turn on the radio, then the  antenna picks up the radio waves and converts them to sound waves that you can hear.   The radio waves that leave the transmitter have different frequencies for each station.Frequencies are the number of times the waves vibrate per second. You tune your radio by choosing a number on the controls.Each number represents a frequency.So if you always tune in the same frequency,you always pick up the same station.

9 Microwaves These have wavelengths of less than 30 cm Microwave ovens work by vibrating the electric field inside the oven.  This causes water molecules to move back and forth.  This movement causes friction which in turn causes HEAT. Despite their small size, they carry a huge amount of energy. One drawback of microwaves is that they can damage living cells and tissue - microwave ovens are surrounded by strong metal boxes that do not allow the waves to escape. Microwaves are also used in cellphones(mobile phones), where they carry your voice back and forth through the air, and radar.

10 Radar - uses radio waves to find the position and movement of objects
      stands for RAdio Detecting And Ranging Devices measure the amount of time it takes for radio waves to get to and then bounce off an object, like a car

11 Recap - There are three uses of radio waves: 1
Recap -  There are three uses of radio waves: 1.  Transmitting information (radio) 2.  Heating food (microwaves) 3.  Measuring speed and distance (radar)

12 Infrared Waves - heat is thermal energy transmitted to you by infrared waves
Hotter objects release more infrared than cooler ones

13 Visible Light Blue = short wavelength Red = long wavelength


15 Ultraviolet Waves = have slightly shorter wavelengths than visible light
They contain enough energy to enter skin cells and can even cause skin damage (sunburn).  UV rays can also kill bacteria and can make some materials FLUORESCE (or glow) like in crime scenes

16 X Rays and Gamma Rays Both are high energy waves and can be damaging if you are exposed to them for long periods X Rays can be used to form images of bone and teeth Gamma Rays - can be used to kill cancer cells (radiation therapy)     *In fiction, gamma rays created the HULK

17 Other ways the waves are used in communication:
1.  AM / FM Radios 2.  Televisions 3. Telephones 4.  Pagers 5.  Satellites



20 1.  Red, green and orange are all part of the electromagnetic spectrum known as  _______________ light. 2.  Microwave ovens work by exciting ________ molecules which then produce heat. 3.  The energy carried by an electromagnetic wave is called ________________________ energy. 4. Which has more energy:          gamma rays or radio waves 5.  Which has more energy:         ultraviolet radiation or X rays 

21 6.  Radar stands for Radio Detecting and ____________
7.  What type of electromagnetic waves are used to treat cancer?  ______________________ 8.  What type of electromagnetic waves are used to create an image of bones and teeth?  _______________ 9.  An electromagnetic wave that behaves like a particle is called a   ________________ 10.  Each number on the dial of a radio represents a station and a  __________________ of the radio waves being transmitted. 

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