1. Electromagnetic Spectrum
Unit 3 Seminar

2. Electromagnetic Wave:
Is a wave that is made up of electrical and magnetic fields that fluctuate together
Electromagnetic waves are generated any time a charged object is accelerated
Image combing your hair on a dry winter day when the comb picks up static charge.
J.Trefil and R. Hazen, The Sciences, 2011, p.126

3. Electromagnetic Spectrum:
The entire array of waves, varying in frequency & wavelength,
but all resulting from an accelerating electrical charge
Electromagnetic waves transfer energy
What has been called radiation
Includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays,

4. Radio waves, visible light, nuclear radiation, and X-rays are also kinds of electromagnetic waves.

5. Look at the diagram and move from left to right and you will see that radio waves have the least energy and gamma rays from nuclear sources have the most energy.

6. Microwaves:
Has wavelengths ranging from approximately 1 meter to 1 millimeter
Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke.
Used for cooking

7. Microwave Ovens
A special electronic device accelerates electrons rapidly & produces microwave radiation which carries energy
The microwaves are guided into the main cavity of the oven
Thus the wave energy remains inside the box until its absorbed by something,
usually by water molecules that get hot from the absorbed energy.

8. Radiation The transfer of heat by electromagnetic radiation
Radiation is the only kind of energy that can travel through the emptiness of space
Doesn’t require any medium to move heat
Can travel through a vacuum
The energy that falls on Earth in the form of sunlight is in the form of radiation
J.Trefil and R. Hazen, The Sciences, 2011, p.81

9. Radio waves have the least energy and gamma rays from nuclear sources have the most energy

10. Your Grandma Pauline has just won a microwave oven in a radio contest
Your Grandma Pauline has just won a microwave oven in a radio contest. When it arrives at her house, it sits on her counter, unused, for a month.
One afternoon, when you visit her, she tells you that she is afraid to use it because "If I stand too close, I'll get radiated!"
Explain to your Grandma the difference between the waves that are used in a microwave oven and the dangerous nuclear radiation she fears.

11. Infrared Radiation
Wavelengths of electromagnetic radiation that extend from a millimeter to a micron
Felt as heat radiation
All warm objects emit infrared radiation
Our skin absorbs radiation and provides a kind of detector
J.Trefil and R. Hazen, The Sciences, 2011, p.133

12. The red-orange areas are the warmest and the white-blue areas are the coldest. .

13. Using the spooky infrared picture of a cat to give some proof to Grandma Pauline that a cat's nose is always cold.

14. If you took a similar infrared photo of your body,
what parts would you expect to show up as brightest orange?
What parts would be blue? Explain.

16. Radio Waves: Ranges from the longest waves To waves a few meters long.
Wavelengths longer than the Earth’s diameter
To waves a few meters long.
Radio wave used for communication can be produced by pushing electrons back and forth in a metal antenna
J.Trefil and R. Hazen, The Sciences, 2011, p.131

17. Radio waves carry signals in two ways
Amplitude modulation ( AM)
Frequency modulation ( FM)

18. After Grandma Pauline starts thinking about electromagnetic waves, she asks you to explain why,
if radio waves and microwaves are both electromagnetic waves, you believe she can’t listen to KROQ- FM on her new oven.