1. Electromagnetic Waves
Target 2-3a
Wednesday, October 25, 2017

2. Target 2-3a
I can describe and model electromagnetic waves by correlating wavelength, frequency, and energy.

3. It all starts with KINETIC ENERGY
Recall that atoms can vibrate
Atoms with more kinetic energy vibrate faster
If atoms vibrate fast enough, they can actually move
Vibrations are how we observe energy traveling from one place to another.

4. Vibrations and Waves
When energy travels, vibrations follow one another in waves
Ex) Waves of water on an ocean shore
Ex) Electricity running through a wire
Ex) Light traveling from the sun to our eyes
Ex) Sound traveling from a piano to our ears

5. Types of Waves Mechanical Waves must travel through matter
Sound waves
Earthquakes
Water waves
Electromagnetic Waves do not need to travel through matter
Electromagnetic = Light!

6. Electromagnetic Waves
Electromagnetic = electricity + magnetism
Electric fields and magnetic fields exist throughout the universe, so electromagnetic waves exist throughout the universe
Different forms of electromagnetic waves come together to create the electromagnetic spectrum

7. Measuring a Wave

8. Amplitude Amplitude = the height of the wave
Measured in distance (meters) but sometimes have their own measurements (ex. Decibels)
Higher amplitude = more intense wave

9. Wavelength Wavelength = the length of a wave from CREST to CREST
Measured as a distance (meters)
This is the length of one cycle of the wave

10. Frequency Frequency = the number of cycles in one second
Higher frequency = shorter wavelength
Higher frequency = higher energy

11. Frequency
Frequency = How many waves travel past a specific point in one second
Measured in Number per Second (Hz)
Higher frequency = lower wavelength
Higher frequency = higher energy

12. Radio Waves Also called cosmic waves
Wavelength can be the length of a football field  diameter of Earth
f=102
Long wavelengths allow them to travel through almost anything without being absorbed
Used to transmit messages and to examine distance objects in the universe

13. Microwaves Wavelength from 1mm  1 foot f=1010
Medium wavelength allows them to travel through many materials, but they leave more interference than radio waves
Used in cell phones, satellites, and weather forecasting equipment

14. Infrared Wavelength of a grain of sand f=1012
We perceive some infrared energy as heat
Infrared energy cannot travel through solid objects but can be used to detect solids – and even their temperatures!
Used in remote controls, heat cameras, and some telescopes

15. Visible Light Wavelength about the size of bacteria f=1015
Each color we see has a slightly different wavelength
We can detect colored light with our eyes based on which wavelengths are absorbed or reflected by objects around us

16. Visible Light

17. Ultraviolet Light Wavelength of very large molecules (like proteins)
Some animals can see UV light
UV light is the lowest frequency that is regularly absorbed and harmful to living things (ex. sunburns and skin cancer)
UV light cannot travel through solids or dense gases (like the ozone layer)

18. X-Rays Wavelength of a small molecule (water) f=1018
Cannot travel through solids or dense gases
The earth’s atmosphere protects us from x-rays
Used to create x-ray photographs (denser substances like bones absorb more x-rays, while less dense substances like skin and muscles allow some x-rays to pass through)

19. Gamma Rays Wavelength of an atomic nucleus f=1022
Highest energy and frequency of any waves
Created by nuclear explosions, lightning, radioactivity, and intense behavior from stars
Cause extreme damage to living cells
But this can be useful in fighting cancer cells

20. Energy from our Sun 43% visible 49% infrared 7% ultraviolet
Less than 1% gamma, x-ray, radio, and micro waves

21. Exit Ticket
Which form of electromagnetic energy is the lowest-energy wave?
Sketch a wave. Label the WAVELENGTH and the AMPLITUDE.

22. WAVES
all
about
Wavelength =
Crest
Amplitude =
Frequency =
target 2-3a

23. THE ELECTROMAGNETIC SPECTRUM
ƒ=102________________________
As big as… used for…
ƒ=1010_______________________
As big as… used for…
ƒ=1012_______________________
As big as… used for…
ƒ=1015_______________________
As big as… used for…
ƒ=1016_______________________
As big as… used for…
ƒ=1018_______________________
As big as… used for…
ƒ=1022_______________________
As big as… used for…