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 = λ x f λ = c / f f = c / λ

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 (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!

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

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!