Electromagnetic Radiation

1
Electromagnetic Radiation
If you would like to hear the text, click here ?
Lesson 1
Introduction to Electromagnetic Radiation
Lesson 2
Where does EM radiation come from?
Lesson 3
Emission Absorption Spectra
Click a button to begin!
If at any time you need to exit the lesson, press
Esc.
2
Introduction to Electromagnetic Radiation
If you would like to hear the slides text during
the lesson, click here ?
What do these pictures have in common?
Next
Back
3
You may have thought most of these items use
electricity, or they are all types of waves. You
are correct. Most importantly, these pictures
are similar in that they are all types of
electromagnetic (EM) radiation.
Do you know any other types of EM radiation?
Click here to see other types of EM radiation!
Next
Back
4
Types of EM radiation
Visible Ultraviolet X-ray Gamma

• Radio
• Microwave
• Infrared

Back
5
Objectives

• You will be able to
• Diagram parts of the EM wave.
• Arrange types of EM radiation in order of
  wavelength.

• You are meeting these standards
• PA 3.4.10 C
• NSTA 2 3

Next
Back
6
James Clerk Maxwell was the first to predict EM
waves, by deriving the waves form from electric
and magnetic equations. These waves were
later confirmed by Heinrich Hertz
Maxwell
Click their pictures to learn more about them!
Next
Back
Hertz
7
Here is a diagram of an EM wave. You can see
that an EM wave is actually made up of two parts,
the electric part, shown in red, and the magnetic
part, shown in black. These two waves travel
perpendicular to each other.
Click here to run a wave propagation simulation!
Next
Back
8
Each of these wave-parts have regular properties
of a wave, including wavelength, amplitude, and
frequency.
What is the mathematical relationship between
wavelength and frequency?
Click here for the answer!
Next
Back
9
c ? f
The mathematical relationship between wavelength
(?) and frequency (f) is an inverse relationship.
C is the speed of light, 3.0 x 108 meters per
second. EM radiation travels at the speed of
light.
Back
10
There are several kinds of EM radiation. They
are arranged by wavelength, from radio with the
longest wavelengths to gamma rays with the
shortest wavelengths.
You can see the size of the wavelength of each
type of wave by comparing the pictures below the
wave. Click the picture to learn more about each
type. (Once at the website, click the EM
radiation to see more about it.)
Next
Back
11
Do you like working hands-on? Do you want to know
more?
Are you having trouble? Do you need it broken
down?
Click the pictures to go to the websites!
Next
Back
12
Here is an EM wave. Can you label all of its
parts?
Click here for the answer!
Next
Back
13
How did you do?
Back
14
Can you sort the types of EM radiation from
longest wavelength to shortest wavelength?
Click here for the answer!
Next
Back
15
How did you do?
Visible Ultraviolet X-ray Gamma
Longest wavelength
Radio Microwave Infrared
Back
Shortest wavelength
16
The Wrap-up!
It is important to learn about EM radiation,
because you encounter it everyday every time you
turn on your radio or television, throw a bag of
popcorn in the microwave, or step out into the
sunshine. It is also important to become
educated about EM radiation, because some forms
can be very harmful to living things, such as UV
rays, which cause skin cancer, and gamma rays
from nuclear weapons. In Lesson 2, we will find
out how EM radiation is formed.
Lesson 2
Back
Press Esc to end the lesson.
17
Where does EM radiation come from?
If you would like to hear the slides text during
the lesson, click here ?
What would you do if someone threw a large
bucket of cold water on you while you were
asleep?
Next
18
How would you react? Jump? Cry? Scream?
Gasp? You would definitely become very excited
and you would probably jump up in your bed. Once
you realized who threw the water on you, you
would probably yell at them, releasing that
excited energy. That is exactly what happens to
electrons!
Next
Back
19
Do you need a refresher of Lesson 1?
Lesson 1
Here is a short movie to help you recall what we
know about EM radiation and give you a peek at
what is in store for Lesson 2. Do you want an
extra challenge? Take the quiz that appears once
the movie is over!
Click here to view the movie!
Next
Back
20
Objectives

• You will be able to
• Diagram a quantum leap.
• Restate why EM radiation is released during a
  quantum leap.

• You are meeting these standards
• PA 3.4.10 C
• NSTA 2 3

Next
Back
21
When energy is absorbed by an electron, it jumps
up to a higher energy level, called an excited
state. Electrons do not want to stay in that
higher state. When they return down to a lower
energy level, what do you think happens?
Click here to figure it out!
Next
Back
22
When the electron returns to a lower energy
level, it must release the energy it absorbed.
This energy is in the form of EM radiation.
Do you remember the different types of EM
radiation?
Click here to see the types of EM radiation!
Next
Back
23
Types of EM radiation
Visible Ultraviolet X-ray Gamma
Radio Microwave Infrared
Back
24
Do you like to learn through music? Here is a
song, called Light Moves, about visible light and
the EM spectrum! Click the picture to see the
full list of songs from the CD.
Click here to hear the song!
Next
Back
25
Niels Bohr stated that electrons can only jump
to discrete energy levels, like rungs in a
ladder. These jumps are known as quantum leaps.
Click Bohrs picture to learn more about him!
Bohr
Are you unfamiliar with the term quantum? Click
the Wikipedia picture to read about it!
Energy levels
Next
Back
26
Do you like working with people? Explain, in
your own words, what a quantum leap is to a
friend or family member!
Do you want to make your own quantum leap?
Click here to run the applet!
Next
Back
27
Each time an electron returns to a lower energy
level, it releases energy. The further away from
the nucleus the energy level is, the more energy
it has. As the amount of energy increases, the
emitted radiation is found further to the right
on the EM spectrum (energy is proportional to
frequency).
What is the mathematical relationship between
energy and wavelength?
Click here for the answer!
Next
Back
28
hc E ?
The mathematical relationship between energy (E)
and wavelength (?) is an inverse relationship.
h Plancks constant, 6.624 x 10-34
joule-seconds.
Back
29
Can you diagram a quantum leap and explain why
radiation is released during the leap?
Click here for the answer!
Next
Back
30
How did you do?
Each time an electron returns to a lower energy
level from an excited state, it releases a
certain amount of energy.
Back
31
The Wrap-up!
It is important to understand quantum leaps,
because we can use the elements emitted energy
to identify it. In Lesson 3, we will find out
what the emitted energy looks like.
Lesson 3
Back
Press Esc to end the lesson.
32
Emission Absorption Spectra
If you would like to hear the slides text during
the lesson, click here ?
Can you guess what this is a picture of?
Next
33
What was your guess? Did you say a rainbow? Or
maybe a prism? Good guesses! Visible light can
be broken apart into a rainbow by a prism. This
is actually the spectrum of our Sun. There are
many lines in the spectrum, because there are
approximately sixty elements present at the
surface of the Sun.
Next
Back
34
Do you remember from Lesson 2, that each time an
excited electron returns from an excited state,
it emits radiation? We can often see that
emitted radiation in the form of visible light.
Do you need a refresher?
Lesson 1
Lesson 2
Which color of light has the highest frequency?
Click here for the answer!
Next
Back
35
Violet light has the highest frequency. Remember,
wavelength and frequency have an inverse
relationship. c ? f
Back
36
Objectives

• You will be able to
• Compare and contrast emission and absorption
  spectra.
• Identify an unknown element by its emission
  spectrum.

• You are meeting these standards
• PA 3.4.10 C
• NSTA 2 3

Next
Back
37
Spectrophotometry is the study of the
electromagnetic spectrum. You can use a simple
device, called a spectroscope, to break apart
emitted light into its colors.
Do you want to build your own spectroscope?
Click here to learn how!
Next
Back
38
When you view a excited gas, such as Hydrogen,
through a spectroscope, you will only see a few
colored lines. This is called an emission
spectrum.
Next
Back
39
Each element gives off a unique set of colored
lines, just like each person has a unique
fingerprint.
Next
Back
40
Try out this simulation to get more practice with
emission spectrum.
Click here to run the simulation!
Next
Back
41
Do you remember in Lesson 2 we said that the
energy emitted is the same as the energy
absorbed?
That means if an element (gas) is in-between the
observer and the light source, the element will
absorb the same wavelengths as we saw in the
emission spectrum, leaving black lines where the
emission lines were.
Next
Back
42
Here you can see both the emission and absorption
spectrum of Hydrogen. Notice how the black
absorption lines correspond to the emission lines.
Next
Back
43
Try out this simulation to get more practice with
absorption spectrum.
Click here to run the simulation!
Next
Back
44
Scientists can use the fact that elements absorb
EM radiation to determine the composition of the
sun. They look at the suns spectrum and compare
the black absorption lines with the emission
spectrum of the predicted elements.
Next
Back
45
Do you need a little more practice? Do you want
to see more about how visible light can be used
to identify stars?
Click here to run the applet!
Next
Back
46
Can you compare and contrast emission and
absorption spectra?
Click here for the answer!
Next
Back
47
How did you do?
Emission spectrum have colored lines which
represent the wavelengths of the energy that was
emitted when electrons return to a lower energy
level.
An absorption spectrum is the inverse of an
emission spectrum. When an element is in-between
a light source and the observer, the element will
absorb the same wavelengths that are present in
its emission spectrum, leaving black lines.
Back
48
Here is an emission spectrum. Can you tell what
element it is?
Click here for the answer!
Next
Back
49
How did you do?
The unknown element was Helium.
Back
50
The Wrap-up!
Emission and absorption spectra are very useful
in identifying elements from other astrological
bodies, such as stars. You will often find that
what you learn in one science class has a lot of
carry-over into other subjects as well.
Back
Press Esc to end the lesson.