9/6/2014
ALEKS Alex H. Yuan - 09/06/2014 3:01:56 PM EDT - Copyright © 2014 UC Regents and ALEKS Corporation
Alex H. Yuan - 09/06/2014 3:01:56 PM EDT
General Chemistry (First Semester) / Chem 110 FA 2014 – CH110 FA14 S25-36 (Dr. Barber)
1.
Understanding the organization of the electromagnetic spectrum
A few different types of electromagnetic radiation are listed in the table below. Complete the table
by ordering these types of radiation by increasing frequency, wavelength, and energy per photon.
For example, select " " in the second column for the type of radiation with the lowest frequency, "
" for the type of radiation with the next higher frequency, and so forth.
type of radiation
order of frequency
order of wavelength
order of energy
microwaves
red light
radio waves
ultraviolet radiation
You can answer this question by using three facts about electromagnetic radiation:
Electromagnetic radiation is divided into different types or bands. Each band includes all
radiation with a particular range of frequency or wavelength. For example, from the diagram
below you can see that electromagnetic radiation with a wavelength between
and
(or a frequency between about GHz and about THz) is called microwave radiation:
All the different types of radiation, taken together, are called the electromagnetic spectrum.
Visible light is electromagnetic radiation with a wavelength between
nm and
.
The exact color of light depends on its exact wavelenth. Light with the longest wavelength
appears red, and light with the shortest wavelength appears deep blue or violet:
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9/6/2014
ALEKS Alex H. Yuan - 09/06/2014 3:01:56 PM EDT - Copyright © 2014 UC Regents and ALEKS Corporation
These are the same colors, in the same order, that you find in a rainbow. Sometimes people
remember the fake name "Roy G. Biv" to remember the traditional seven colors of the rainbow:
Red Orange Yellow Green Blue Indigo Violet
For the purposes of beginning chemistry, you should at least memorize the fact that red light
has the longest wavelength, blue or violet light the shortest, and green light is right in the
middle.
The energy in each photon of any electromagnetic radiation is directly proportional to its
frequency :
The symbol
stands for the Planck constant,
.
What this means is that electromagnetic radiation with a higher frequency has a higher photon
energy, and electromagnetic radiation with a lower frequency has a lower photon energy. For
example, the photon energy of X-rays is much higher than the photon energy of visible light.
And the photon energy of visible light is much higher than the photon energy of radio waves.
Here's the completed table:
type of radiation
order of frequency
order of wavelength
order of energy
microwaves
2
3
2
red light
3
2
3
radio waves
1 (lowest)
4 (highest)
1 (lowest)
ultraviolet radiation
4 (highest)
1 (lowest)
4 (highest)
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