# Chapters 17 & 18 The Electromagnetic Spectrum

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Chapters 17 & 18 The Electromagnetic Spectrum
Do Now: 2 NJ ASK Questions Make a cover page for our next unit: Light, The Electromagnetic Spectrum, & Color The Electromagnetic Spectrum Believe it or not, you are being “showered” all the time, not by rain but by waves. Chapters 17 & 18 popcorn cell phone

Polarized Light

Light Travels as a Wave The Wave Model:

Light Travels as a Particle
The Particle Model: Photoelectric Effect: When electrons change energy levels free electrons are produced… where does this energy go? Energy makes the photons that produce a form of light energy. In 1905 Einstein named the “Photon” which he called “bundles of radiation” Won the Nobel Prize in 1921

So does light travel as a wave or as a particle?
Since there is evidence for both, light is believed to act as both a wave and a particle. The frequency and amount of energy in the photons are responsible for the type of energy produced.

What is the Electromagnetic Spectrum?
The complete range of EM (electromagnetic) waves placed in order of increasing frequency and decreasing wavelengths. All EM waves have different wavelengths and frequencies, but travel at the same speed. EM Spectrum Song

What is the speed at which all EM waves travel?
All EM waves travel at the speed of light! Speed of light = 299,792,458 m/s Can be rounded to: 300,000,000 m/s 300,000 km/s 186,000 mi/s

Tape in NB: Copy and Color visible light colors

Wavelength Size Comparison

All EM waves produce some form radiation! The lower the frequency, the lower the radiation. The higher the frequency, the higher the radiation. EMS YouTube popcorn cell phone

All EM waves produce some form radiation! The lower the frequency, the lower the radiation. The higher the frequency, the higher the radiation. EMS YouTube

Electromagnetic Waves
Transverse-like waves that travel at the speed of light (No medium needed) Consist of traveling electric and magnetic fields Also contain tiny particles called photons which are “packets of light/energy”

Satellites (in space) receive waves and relay signals back to Earth AM/FM Radio, Satellite Radio/TV, GPS AM: Amplitude changes FM: Frequency changes

DO NOW: Draw and complete the chart
Electromagnetic waves travel at the speed of have different consist of Electric fields Magnetic fields Wavelengths Frequencies Light

Microwaves Radio waves with the shortest wavelengths
Used for cell phone communication and radar (radio detection & ranging) Used to cook food

Infrared Rays Felt as heat Used in heat lamps, infrared
cameras (thermograms) medicine, and remotes

Visible Light Portion of the E.M. spectrum that the human eye can see
White light is a mixture of 7 colors: red, orange, yellow, green, blue, indigo, & violet (R O Y G B I V) Largest to Smallest Wavelength

Visible Light Without a light source we cannot see colors! Think About it… Have you ever seen color at night in the dark?? A prism will refract light showing the colors of the visible light spectrum

Ultraviolet (UV) Rays Frequencies just higher than visible light (violet end) Causes sun tans & burns Helps produce vitamin D Can kill cells (good for cleaning germs, bad for skin) Allows bees to see pollinated flowers Dangerous in high doses

X-Rays Can pass through most matter (but not dense objects like bones)
Used to make images of bones Dangerous in high doses

Gamma Rays Produced by radioactive substances and nuclear reactions
Used as cancer treatments Used to diagnose medical conditions Dangerous in high doses Greatest amount of energy

1A. A transverse wave that transfers electrical and magnetic energy.
HW 17.1 1A. A transverse wave that transfers electrical and magnetic energy. B. Travel as vibrations in electric and magnetic fields that move through space at the speed of light. C. Electric field- surrounds every charged particle and produces electric forces that can push or pull on other charged particles. Magnetic Field- produced when a charged particle moves and it exerts magnetic forces that can act on certain materials. 2A. Wave model and particle model of light B. Light strikes a polarizing filter, only some waves pass through. These waves vibrate in only one direction and are called polarized light. C. When light acts like a stream of tiny particles of energy, called photons, the photons can cause electrons to be knocked out of some substances. (Free electrons create energy) This is the photoelectric effect.