1. ELECTROMAGNETIC WAVES

2. Nature of Waves
A disturbance that transfers energy from one place to another is called a wave.
The source of any wave is a vibration.
A substance or region through which a wave is transmitted is called a medium.
Mechanical waves, such as sound waves, require a medium to travel.

3. Transverse Waves
An electromagnetic wave consists of vibrating electric and magnetic fields.
An electromagnetic wave is a transverse wave that transfers electrical and magnetic energy.
Transverse waves do NOT require a medium to travel
Unlike sound waves, electromagnetic waves can travel in a vacuum, which means they can travel through space.
Speed of electromagnetic waves –
300,000,000 meters/second
Takes light 8 minutes to travel from the sun to earth {150 million miles} at this speed.

4. In order to create the vibrating electric and magnetic fields that are characteristic of an electromagnetic wave, electrons must move.

5. How are electromagnetic waves created?
Electrons are arranged in energy levels.
electrons with the lowest energy are found closest to the nucleus
electrons with higher energy are found farther away from the nucleus
If an electron moves closer to the nucleus, energy is released & an electric and magnetic field is created.
These fields form electromagnetic waves.

6. Types of Electromagnetic Waves
Radio waves
Microwaves (a type of radio wave)
Infrared light
Visible light – red, orange, yellow, green, blue, & violet
Ultraviolet light (UV)
X-rays
Gamma rays

7. Electromagnetic Spectrum

8. Electromagnetic Spectrum

9. Electromagnetic Spectrum
Radio Waves
Have the longest wavelengths and lowest frequencies of all the electromagnetic waves.
Used in radios & TVs
A radio picks up radio waves through an antenna and converts it to sound waves.
Each radio station in an area broadcasts at a different frequency. # on radio dial tells frequency.
MRI (MAGNETIC RESONACE IMAGING)
Uses short wave radio waves with a magnet to create an image

10. MRI Images

11. Electromagnetic Spectrum
Microwaves
Microwaves – have the shortest wavelengths and the highest frequency of the radio waves.
Used in microwave ovens –
Microwaves are absorbed by water, fats and sugars. When they are absorbed they are converted directly into atomic motion = heat.
Metal reflects microwaves, which is why metal pans do not work well in a microwave oven.

12. Electromagnetic Spectrum
Microwaves
Other uses –
Used by cell phones and pagers.
RADAR (Radio Detection and Ranging)
Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return

13. Electromagnetic Spectrum
Infrared Rays
Infrared = below red
Shorter wavelength and higher frequency than microwaves.
You can feel the longest ones as warmth on your skin
Warm objects give off more heat energy than cool objects.

14. Electromagnetic Spectrum
Infrared Rays
Thermogram –a picture that shows regions of different temperatures in the body.
Temperatures are calculated by the amount of infrared radiation given off.
Therefore people give off infrared rays.
Other uses –
cooking - special lamps that emit thermal infrared waves are often used in fast food restaurants
T.V. remote controls

15. Electromagnetic Spectrum
Infrared Rays

16. Electromagnetic Spectrum
Visible Light
Visible spectrum – these are e/m waves we can see
When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors –
Red, Orange, Yellow, Green, Blue, & Violet
Longest wavelength = red light
Shortest wavelength = violet (purple) light

17. LIGHT: What is it? Atoms -
electrons release light when falling down to lower energy levels
photons - packets of energy released when the electrons fall
Light = a stream of photons, or packets of energy, released when electrons move from higher energy levels to lower energy levels

18. Electromagnetic Spectrum
Ultraviolet Light
Shorter wavelength and higher frequency than visible light
Carry more energy than visible light
Use in hospitals to kill bacteria cells – sterilization of equipment
Causes your skin to produce vitamin D – good for teeth & bones (helps with the absorption of calcium)
Too much can cause skin cancer
Use sun block to protect against (UV rays)

19. Electromagnetic Spectrum
X-Rays
Shorter wavelength and higher frequency than UV-rays
Carry a great amount of energy
Can penetrate most matter
Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed)
Too much exposure can cause cancer
lead vest at dentist protects organs from unnecessary exposure
Used by engineers to check for tiny cracks in structures
The rays pass through the cracks and the cracks appear dark on film.

21. Electromagnetic Spectrum
Gamma Rays
Gamma rays have the smallest wavelengths and the most energy of any other wave in the e/m spectrum.
They are generated by radioactive atoms and in nuclear explosions.
They are also produced by such violent events as supernova explosions (the way massive stars die).
Gamma-rays are used to kill cancerous cells
Gamma-rays travel to us from outer space & are absorbed by the Earth's atmosphere.

22. SUMMARY
All electromagnetic waves travel at the same speed – 300,000,000 m/s in a vacuum
They all have different wavelengths and different frequencies.
Longer wavelength  lowest frequency
Shorter wavelength  highest frequency
The higher the frequency the higher the energy.