Electromagnetism

1. Training of Trainers for Grade 10 of the K
to 12 Enhanced Basic Education
Program
April 27 – May 2, 2015
(Luzon Cluster)

2. Spiraling of concepts
Module 2 Competencies
Module 2 activities
Activity 2: Now you go! Now you
won’t!
Discussion
Essential Characteristics of Science
Inquiry
Outline of Presentation

3. In Grade 7
EM spectrum consists of various types of waves.
The higher the frequency, the shorter the wavelength.
High energy EM waves have high frequency and short wavelengths.

4. In Grade 8
visible light
Light is composed of different colors.
The arrangement of colors of light shows the
hierarchy of the colors’ corresponding energy.

5. In Grade 10
Applications of the
different EM waves
Image Credit: http://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html

6. TRUE OR FALSE:
1.Electromagnetic waves carry energy.
2.An electromagnetic wave is a longitudinal
wave.
3.Electromagnetic waves can travel in an
empty space.
4. Sound waves are electromagnetic
waves.
5. Different colors of light have the same
amount of energy.
Sample Pre-assessment

7. The learners should be able to:
 compare the relative wavelengths of different
forms of electromagnetic radiation
 explain uses of the different forms of EM
radiation
 create models on how materials react to EM
radiation other than light (e.g. glass is opaque
to some UV rays)
 explain the effects of EM radiation to living
things
Competencies

8. 1. How it came about… [Contribution of
different scientist]
2. Now you go! Now you won’t! [Materials
that allow/block EM waves]
3. Sound check…[Producing and detecting
radio waves]
4. Then there was sound… [Parts of a radio
transmitter and receiver]
5. It’s getting hotter [About infrared radiation]
6. Screen the UV out [About UV radiation]
Activities in Module 2

9. Hey Hans, the opposite
could be true! A changing
magnetic field produces
an electric field.
Hans Christian Oersted
1777-1851
James Clerk Maxwell
1831-1879
OMG! The compass needle
move near the current-
carrying wire. This shows
electric current creates
magnetic field.
Activity 1: How it came about…
http://www.rare-earth-magnets.com/hans-christian-oersted/
You both got it right! An
electromagnetic wave exists
when the changing magnetic
field causes a changing
electric field, which then
causes another changing
magnetic field, and so on.
Heinrich Hertz
1857-1894 http://en.wikipedia.org/wiki/Heinrich_Hertz
http://simple.wikipedia.org/wiki/Michael_Faraday
Michael Faraday
1791-1867
http://soulconnection.net/glossary_in_depth/maxwell.html
You got it right
Maxwell. I proved
the existence of EM
waves!
Image credit:

10.  A moving charge creates
magnetic field.
 A changing magnetic field
causes a changing
electric field.
Image credit:
http://www.school-for-
champions.com/science/magnetic_field_movin
g_charges.htm#.VThZiyaKCM8
Image credit:
http://electrical4u.com/faraday-law-of-
electromagnetic-induction/

11.  The successive production of electric and
magnetic field results to the creation EM wave.
 An EM wave propagates outward from the
source.
Image credit:
http://www.astronomynotes.com/light/s2.htm

12.  The electric and magnetic fields vibrate at right angles to
the direction the wave travels so it is a transverse wave.
Image credit:
http://www.astronomynotes.com/light/s2.htm

13. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox
/emspectrum1.html
Newton set up a prism near his window,
and projected a beautiful spectrum 22 feet
onto the far wall. Further, to prove that the
prism was not coloring the light, he
refracted the light back together.
Image credit:
http://www.webexhibits.org/colorart/bh.html
The modern
understanding
of light and
color begins
with Isaac
Newton.

14. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Image credit:
http://coolcosmos.ipac.caltech.e
du/cosmic_classroom/ir_tutorial
/discovery.html
Frederick William
Herschel
(1738 - 1822)
In 1800 he performed a famous experiment
where he tried to measure the temperature of
different colours of the spectrum by placing a
thermometer on each colour. He found to his
amazement that the hottest part of the spectrum
was in a place where there was no colour at
all. It was a spot beyond the red end of the
spectrum. For the first time it was possible to
talk about invisible light. This hot light became
known as Infra Red (below the red) because it
was shown to have longer wavelength than
visible light. [http://www.krysstal.com/spectrum.html]

15. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Johann Wilhelm Ritter
(1776 - 1810)
Image credit:
http://coolcosmos.ipac.caltech.edu/cos
mic_classroom/classroom_activities/ritt
er_bio.html
In chemistry at that time there was a rumour that blue
light was more efficient at initiating chemical change
than red light. Ritter tried to measure the speed at
which silver chloride broke down with different colours.
He proved that blue light was indeed more efficient that
red light. He was amazed, however, that the most
vigorous reactions took place in the region beyond the
violet where nothing could be seen.
This new radiation was originally called Chemical Rays
but is now called Ultra Violet (beyond the violet). Ultra
Violet differs from visible light only in its wavelength
which is shorter. [http://www.krysstal.com/spectrum.html]

16. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Heinrich Rudolf Hertz
(1857 - 1894)
Image credit:
http://en.wikipedia.org/wiki/Hein
rich_Hertz
He set up electric circuits that produced
oscillations and managed to produce
electromagnetic radiation with a
wavelength of 66cm (over a million times
longer than light). This radiation could be
picked up by other circuits set up quite a
distance away. The new radiation was first
called Hertzian Waves; this became
Radiotelegraphic Waves after Marconi. We
now call them Radio Waves.
[http://www.krysstal.com/spectrum.html]

17. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Perry Spencer (1894 - 1970) invented
the microwave oven
In 1945, Percy Spencer was experimenting with a new
vacuum tube called a magnetron while doing research
for the Raytheon Corporation. He was intrigued when
the candy bar in his pocket began to melt, so he tried
another experiment with popcorn. When it began to
pop, Spencer immediately saw the potential in this
revolutionary process. In 1947, Raytheon built the first
microwave oven, the Radarange.
[http://science.howstuffworks.com/innovation/scientific-experiments/9-things-
invented-or-discovered-by-accident2.htm]
The scientists discovered the cosmic
microwave background radiation. This
radiation, which fills the entire Universe, is
believed to be a clue to it's beginning,
something known as the Big Bang.
Arno Penzias and Robert Wilson

18. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Wilhelm Conrad Roentgen
(1845 - 1923)
On the night of 5 November 1895, he noticed a glow
coming from a chemical called barium platinocyanide.
This chemical glowed whenever the tube was on, even
if he put cardboard between it and the tube.
Roentgen went on to show that the glow was caused by
a highly penetrating but invisible radiation given off by
the tube. It passed through paper, thin sheets of metal,
flesh. It could ionise gases and had wave properties like
light but only much shorter wavelengths.
The new radiation was called X-Rays because of their
mysterious properties. Roentgen refused to patent the
discovery or make any financial gain out of it but he
was awarded the first ever Nobel Prize for Physics.
[http://www.krysstal.com/spectrum.html]
Image credit:
http://www.two-views.com/article_Rontgen.html

19. Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/ems
pectrum1.html
Villard discovered gamma radiation in 1900, while
studying radiation emitted from radium. Villard knew
that his described radiation was more powerful than
previously described types of rays from radium, which
included beta rays, first noted as "radioactivity" by Henri
Becquerel in 1896, and alpha rays, discovered as a
less penetrating form of radiation by Rutherford, in
1899. However, Villard did not consider naming them as
a different fundamental type. Villard's radiation was
recognized as being of a type fundamentally different
from previously named rays, by Ernest Rutherford, who
in 1903 named Villard's rays "gamma rays" by analogy
with the beta and alpha rays that Rutherford had
differentiated in 1899.
[http://en.wikipedia.org/wiki/Gamma_ray]
Paul Ulrich Villard
(1860 - 1934)
Image credit:
http://en.wikipedia.org/wiki/Paul_Ulrich_Villard

20. EM spectrum is a continuum of EM waves arranged according to
frequency and wavelength.
It shows a gradual progression from the waves of lowest frequency to
the waves of highest frequency or vice versa.
The different EM waves do not have exact dividing region.

21. Module 2: Electromagnetic Spectrum
Motivation:
Call me maybe
Hey I just met you
And this is crazy
But here's my number
So call me maybe
(insert number here)

22. Cell phones uses microwaves to transmit and receive
information.
Remote control of RC cars also sends a control signal
using radio waves.

23. Now you go!
Now you won’t!
Activity 2

24.  Identify materials that can block or allow radio
waves.
 Compare the speed of the car when the
transmitter is without cover and when it is
covered with different materials.
Objectives

25. Questions to be investigated
What materials allow radio waves to
pass through them?
What materials block radio waves?

26. Materials
aluminum foil
transparent plastic
colored paper
wax paper
kitchen paper towel
Latex gloves
Remote- controlled
car

27. Procedure
2 Wrap the antenna around the remote
control. Secure it with a twist-tie wire
or rubber band.
1 Test the RC car if it is working.

28. Procedure
3 Use the remote control to make the toy
car run. [The car should run in a straight path. If
not, place the car between two planks of wood or
meter sticks.]
Image of car:
http://www.dreamstime.com/royalty-free-stock-photo-red-german-expensive-car-collectible-toy-cabriolet-
isolated-white-background-image40543185

29. Procedure
4 Choose a distance for the car to travel
on. Use a stopwatch (cell phone) to
get the time it took the car to travel the
distance. Maintain the distance
between the car and the remote
control. Press once the “forward
button” and don’t release it until the
car reached the ‘finish line’ of the
distance you set.

30. Procedure
5 Start measuring the time it took the car
to cover the distance you set with the
remote control without cover first.
Record the time in Table 1.
6 Wrap the remote control one at a time
with the different materials. Make sure
that it is completely covered.

31. Make sure you know where the forward
button is.

32. Materials to test:
The materials should be of the same size so the remote
control will be wrapped with equal thickness.
The materials will be used by other group.
Please unfold them carefully after each
use.

33. Procedure
7 Record in Table 1 the time it took the
car to cover the distance you set with
the remote control covered with
different materials.

34. Material
covering the
remote control
RC car time of
travel (s)
Observations
No cover
Colored Paper
Wax Paper
Kitchen paper
towel
Transparent
Plastic
Aluminum Foil
Latex gloves
Table 1

35. 1. Which of the materials that cover the remote control allows the
radio waves to pass through? What evidence shows radio waves
pass through these materials?
2. Which of the materials that cover the remote control blocks the
radio waves? What evidence shows radio waves was blocked by
these materials?
3. What kind of materials allowed radio waves to pass through?
4. What kind of materials blocked radio waves?
5. What do the results of the activity tell about the characteristics of
radio waves?
6. Compare the time taken by the car to travel the distance you set
when the remote control was not covered to the time when the
remote control was covered with different materials. Are they the
same? What does this tell about the strength of the signal sent by
the remote control when it hits the material covering it?
Guide Questions:

36. 1. Which of the materials that cover the remote control allows the
radio waves to pass through? What evidence shows radio waves
pass through these materials?
2. Which of the materials that cover the remote control blocks the
radio waves? What evidence shows radio waves was blocked by
these materials?
Guide Questions:
aluminum foil
transparent plastic
colored paper
wax paper
kitchen paper towel Latex gloves
The RC car moved.
The RC car did not move.

37. 3. What kind of materials allowed EM waves to pass through?
4. What kind of materials blocked EM waves?
Guide Questions:
Paper (cellulose)
colored paper
wax paper
kitchen paper towel
Rubber (elastomers)
Latex gloves
Plastic (polyethylene)
transparent plastic
Aluminum - Metallic
aluminum foil

38. 5. What does the result of the activity tells about the characteristic of
radio waves?
6. Compare the time taken by the car to travel the distance you set
when the remote control was not covered to the time when the
remote control was covered with different materials. Are they the
same? What does this tell about the strength of the signal sent by
the remote control when it hits the material covering it?
Radio waves can be blocked by some materials.
Radio waves can pass through some materials.
No
The signal can be weakened by the material covering the
remote control.
Guide Questions:

39. Discussion
radiowaves
transmitting
antenna
receiving antenna
(not visible outside the car)
receiving
antenna
Receiver - An antenna and circuit board inside the toy receives signals from the
transmitter and activates motors inside the toy as commanded by the transmitter.
Transmitter
sends a control signal to the receiver
using radio waves

40. Discussion
Transmitter:
sends a control signal to the receiver
using radio waves
Power supply: Provides the necessary
electrical power to operate the transmitter.
Transmitter consists of several elements
that work together to generate radio
waves that contain useful information

41. Three things happen to EM waves when it encounters a
barrier. It can bounce (reflectance or scattering), pass
through (transmittance), or just plain stop (absorbance).
Discussion
Image credit:
https://sites.google.com/site/waveslightandsoundunit/03---unit-lessons/04---light-waves

42. When a radio wave reaches an obstacle, some of its energy is absorbed
and converted into another kind of energy, while another part is
attenuated and continues to propagate, and another part may be
reflected.
Discussion
Attenuation is when a signal's power is reduced as it is being
transmitted.
Attenuation increases with a rise in frequency or in distance. Also, when
a signal collides with an obstacle, the level of attenuation
depends strongly on which type of material the
obstacle is made of.

43. What is Attenuation Coefficient?
• The attenuation coefficient is the level by which a material will
block or interfere with radio waves.
• This coefficient depends heavily on the thickness and
composition of the material.
• Cardboard, paper, many plastics, water, and glass are all
substances with very low attenuation coefficients. In
addition, wood, brick, and cement have a limited effect on
making radio waves blocked.
• However, metallic compounds, steel-reinforced concrete and
the Earth reflect signals, preventing radio signals from
passing through.
Discussion

44. Properties of media
The weakening of signal strength is largely due to the properties of the
medium that the wave is passing through. Here is a table showing attenuation
levels for different materials:
Materials
Degree of
Attenuatio
n
Examples Materials
Degree of
Attenuatio
n
Examples
air none Open space bricks medium walls
wood low Door , floor,
partition
plaster medium partitions
plastic low partition paper high Rolls of paper
glass low Untinted windows concrete high Load-bearing
walls, floors
Tinted glass medium Tinted windows Bullet proof
glass
high Bullet proof
windows
water medium aquarium metal Very high Metal cabinet,
elevator cage
Living
creatures
medium Crowds, animals,
people, plants
Source:
http://en.kioskea.net/contents/832-propagation-of-radio-waves-802-11

45. 2 Types of matter (substance) that
affect Radio waves
Conductors
Copper
Aluminum
Silver
Gold
Insulators
(Dielectrics)
Paper
Plastic
Teflon
Glass
Ceramic
Dry wood
As the radio wave travels through the
dielectric material some of the energy is
absorbed generating heat and some of the
radio waves travel through and comes out
of the other side.
If the material is metal, almost all of
the radio waves are reflected within
the first few atoms of the material. A
small amount of energy is absorbed
by the silver atoms and converted to
heat.

46. Students can take the investigation further by
comparing the ability of the same materials in
blocking other EM Waves .
Extension Activity
Ionizing
radiation
Non-ionizing
radiation

47. Students can take the investigation
further by controlling variables such as
the thickness of materials.
Extension Activity

48. Characteristics Activity 2: Now you go! Now you won’t!
Engaging in scientifically-
oriented questions
Gathering evidence
5 Essential Characteristics of Scientific Inquiry
What materials allow/block radio waves?
Observe the car if it moves or not
Infer that if the car moves, then the radio waves
emitted by the transmitter pass through the
material covering it
Infer that if the car did not move, then the radio
waves emitted by the transmitter did not pass
through the material covering it

49. Characteristics Activity
Providing explanations based
on evidence and scientific
knowledge
Evaluating explanations
Justifying and communicating
explanations
5 Essential Characteristics of Scientific Inquiry
If the material blocking the radio
wave is metal, almost all of the
EM waves are reflected.
If the material blocking the EM
wave is dielectric, some of the EM
waves are absorbed and some are
transmitted.