1. Electromagnetic Waves

2. About Electromagnetic Waves
Electromagnetic Waves – waves that carry energy without requiring a medium
- produced by changing electrical and magnetic fields
- behave as transverse waves
- the electrical and magnetic fields move perpendicular to the direction of energy travel
Because they require NO MEDIUM, electromagnetic waves can pass through space
The energy carried by electromagnetic waves is called electromagnetic radiation

3. About Electric and Magnetic Fields
Electric and Magnetic fields are areas in space where there either an electric or magnetic force
Whenever you have a changing magnetic field you will have a changing electric field and vice versa
- when one field changes, so does the other

4. The Speed of Electromagnetic Waves
The speed of all electromagnetic waves in a vacuum (outer space) is equal to the speed of light
Speed of Light = 300,000,000 m/s
When entering our atmosphere, or changing mediums, electromagnetic waves slow down
- even when slowing down, electromagnetic waves travel a million times faster than the speed of sound.
We can calculate the wavelength and frequency of all electromagnetic waves using the same equations as before
- Because we are working with very large and very small numbers we need to understand scientific notation

5. Scientific Notation
Scientific notation is a shorthand used in science and math to write really large numbers in a shorter form using exponents.
How It Works:
Place a decimal point after the first non-zero number in the large number
Write out all the digits in between the first and last non-zero numbers in the large number
Multiply by 10e, where e is the number of times you need to move the decimal to write the whole number
-- if e is positive, you move the decimal to the right
-- if e is negative, you move the decimal to the left

6. Practice With Scientific Notation
Write the following whole numbers in Scientific Notation
456,000   
Write the following as whole numbers:
a) 5.15 x 108 
b) x 
c) 3.00 x 102 
4.56 x 105
7.204 x 10-3
1.0 x 10-8
300

7. Multiplying and Dividing In Scientific Notation
Multiplying and dividing in scientific notation is very easy!
Just split the equation into two parts: the decimal and the 10 to the exponent.
For Division
Divide the top decimal by the bottom decimal
Subtract the bottom exponent from the top exponent
For Multiplication
Multiply the decimals together
Add the exponents together

8. Practice Multiplying and Dividing Using Scientific Notation
(3.33 x 107)
(1.11 x 105)
2. (5.29 x 10-9) x (8.00 x 104)
3.00 x 102
4.232 x 10-4

9. Using Scientific Notation to Calculate Wavelength and Frequency
Remember that the speed of electromagnetic waves is pretty much equal to the speed of light.
We use the letter c to represent the speed of light.
Therefore, our three wave equations are now:
c = λ x f
λ = c / f
f = c / λ

10. Practice Problems Practice Problem 1:
What is the wavelength of an electromagnetic wave with a frequency of 6.00 x 1016 Hz?
Practice Problem 2:
What is the frequency of an electromagnetic wave with a wavelength of 333 nm? (1 nm = 1 x 10-9 m)

11. The Electromagnetic Spectrum
Although all electromagnetic waves have the same speed, they have different wavelengths and frequencies.
Electromagnetic waves with the longest wavelengths have the smallest frequencies.
Electromagnetic waves with the largest frequencies have the shortest wavelengths.
We classify electromagnetic waves on a spectrum, from longest wavelength (smallest frequency) to shortest wavelength (highest frequency)

12. Electromagnetic Spectrum Diagram
Increasing Frequency
Increasing Wavelength

13. List of Electromagnetic Waves
Most Energetic
Highest Frequency Gamma Rays Shortest Wavelength
X-Rays
Ultraviolet Rays
Visible Light
Infrared Rays
Microwaves
Lowest Frequency Radio waves Longest Wavelength
Least Energetic

14. Uses of Electromagnetic Waves
Radio Waves
-- longest wavelength, lowest frequency
-- used to transmit radio signals
Microwaves
-- actually a type of high-frequency radio wave
-- still has a very low frequency, long wavelength
-- used in radar
-- used in ovens
-- when water molecules in food absorb the energy from microwaves, they heat up, cooking food

15. Uses of EM Waves (Cont’d)
Infrared Rays
-- just below “red” in the visible spectrum
-- often felt as heat
Visible Light
-- less than 1% of the EM spectrum is visible light
-- range from longest wavelengths (red) to shortest wavelengths (violet)
-- this is what we see!

16. Uses of EM Waves (Cont’d)
Ultraviolet Rays
-- means beyond violet
-- small doses are used to produce Vitamin D
-- comes from the sun
-- large doses can kill and damage cells
-- often used to sterilize equipment in hospitals
X-Rays
-- can pass through soft tissue
-- used to see pictures of bones inside body

17. Uses of EM Waves (Cont’d)
Gamma Rays
-- highest-energy electromagnetic wave
-- can penetrate most tissues
-- creating the Incredible Hulk
-- highest frequency, shortest wavelength
-- often given out by radioactive substances
-- sometimes used in medicine, but because they are so damaging, need to be seriously controlled
The End of it All!