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Electromagnetic Waves

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

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

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

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

Practice With Scientific Notation

- Write the following whole numbers in Scientific

Notation - 456,000 ?
- .007204000 ?
- .00000001 ?
- Write the following as whole numbers
- a) 5.15 x 108 ?
- b) 3.662 x 10 -4 ?
- c) 3.00 x 102 ?

4.56 x 105

7.204 x 10-3

1.0 x 10-8

515000000

.0003662

300

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

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

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 ? x f ? c / f f c / ?

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)

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)

Electromagnetic Spectrum Diagram

Increasing Frequency

Increasing Wavelength

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

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

Uses of EM Waves (Contd)

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!

Uses of EM Waves (Contd)

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

Uses of EM Waves (Contd)

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!