24.1 the electromagnetic spectrum pp. 522 - 527 mr. richter
TRANSCRIPT
24.1 The Electromagnetic Spectrum
pp. 522 - 527
Mr. Richter
Agenda
Warm Up
Review HW
Notes: About Electromagnetic Waves The Electromagnetic Spectrum
Low-Energy EM Waves Visible Light High-Energy EM Waves
Objectives: We Will Be Able To…
Learn the relationship among the frequency, wavelength and energy of light.
Identify the different kinds of electromagnetic waves, and rank them in order of energy.
Warm-Up:
To read your book, you move 6 times closer to the lamp than you were before.
How much brighter does the light appear to be on the page of the book?
About Electromagnetic Waves
About Electromagnetic Waves
Electromagnetic (EM) waves are formed when moving electrons change the electric and magnetic fields around them.
Like a hand shaking a magnet.
Sources of EM waves emit oscillating electric and magnetic energy.
Obviously, EM waves are non-mechanical waves.
The Electromagnetic Spectrum
The Electromagnetic Spectrum
There is a wide range of frequencies of EM waves called the electromagnetic spectrum.
Remember, low frequency means:
Low energy
Long wavelength
The Electromagnetic Spectrum
The EM spectrum contains seven types of waves, in order from low to high frequency: radio microwaves infrared visible light ultraviolet light x-rays gamma rays
All of the spectrum is invisible to us except for visible light.
Just like there are some sounds we can’t hear.
The Electromagnetic Spectrum
The EM spectrum contains seven types of waves, in order from low to high frequency: radio microwaves infrared visible light ultraviolet light x-rays gamma rays
The EM spectrum is broken up into two halves: low-energy and high-energy.
High-energy waves can remove an electron from an atom (= radiation = dangerous!)
Low-energy waves cannot.
Low-Energy EM Waves: Radio and Microwaves
Radio waves are the lowest-frequency waves. Wavelengths can be kilometers
long!
Microwaves Used by cell phone and
microwave ovens Microwave ovens are tuned to
the natural frequency of water molecules. (Resonance!)
Low-Energy EM Waves: Infrared
Infrared waves are just below the frequency of visible light.
They are sometimes referred to as radiant heat.
Although we can’t see them, we can feel them.
We have designed electronic equipment to help us see them.
Low-Energy EM Waves: Visible Light
Visible light makes up a very small portion of the EM spectrum.
Wavelengths range only from about 400 – 700 nanometers. Not much bigger than
individual atoms.
Red: long wavelength, low frequency
Violet: short wavelength, high frequency.
High-Energy EM Waves
Ultraviolet light Easily absorbed by humans. We need
some, but not too much.
X-rays Pass easily through skin, but not
through bones. Dangerous in large amounts.
Gamma rays have the highest frequency. Lots of energy! They can completely push electrons
out of an atom!
Wrap-Up: Did we meet our objectives?
Learn the relationship among the frequency, wavelength and energy of light.
Identify the different kinds of electromagnetic waves, and rank them in order of energy.
Homework
p. 527 #1, 2, 4, 5