Understanding Electromagnetic Waves and propagation

!
Opening Prayer
Our Lord God in heaven. Thank you for the new day you've bestowed
upon us. Until this moment, we still have our borrowed life and strength
from you. We worship and praise Your Holy Name.
This moment, we will continue to study and acquire new knowledge. May
you bless your students with witty brain to think fast and an inquiring mind
to be curious on whatever knowledge they will learn today. Most
importantly bless them with Your wisdom and a heart that will follow your
commandments in order for them to become worthy in their studies.
We hope that you heard our prayer.
We ask all of these. In the name of Jesus Christ, our Saviour.
Amen.

Science Intervention:
•What is momentum?
•What is collision?
•What are the 3 types of
collision?

•Momentum can be defined
as "mass in motion." All
objects have mass; so if an
object is moving, then it has
momentum - it has its mass
in motion.

Collision is any event in
which two or more
bodies exert forces on
each other in a relatively
short time.

Elastic collision
Inelastic collision
Perfectly inelastic

Objectives for the Week
•Compare the relative wavelengths of different forms
of electromagnetic waves;
•Cite examples of practical applications of the
different regions of EM waves, such as the use of
radio waves in telecommunications;
•Explain the effects of EM radiation on living things
and the environment;

Center of Gravity for Nonuniform Objects
•Non-uniform objects
are those that have
irregular shapes. The
center of gravity of a
non-uniform object
may be determined
by hanging and
balancing it or by
using the plumb line
method.

Center of Gravity for Nonuniform Objects
•To find the CG by
hanging and balancing,
tie a piece of string or
wire to suspend the
object as shown in the
figure

Understanding Electromagnetic Waves and propagation

Where is the
center of
gravity of the
two persons?

•The base of support has
been defined as the
horizontal stride width
during the double-
support phase when both
feet are in contact with
the ground and the whole-
body center of gravity (CG)
remains within the BOS

Increasing the area of the base will also increase the stability of
an object, the bigger the area the more stable the object.

•Muscles are used
extensively to balance
the body in the front-
to-back direction.
•While bending in the
manner shown,
stability is increased
by lowering the center
of gravity.
•Stability is also
increased if the base is
expanded by placing
the feet farther apart.

Which do you think is the safest
stool to use in a laboratory?

• The effect of size of the base
is shown by the three stools.
• The centres of gravity of all
the stools are the same
height above the ground but
because stool (c) has a
much smaller base it topples
over if they are all tilted to
the same angle while the
other two stools return to a
level position.
• Notice that the centre of
gravity is not inside the
material of the stool.

• Line Of Gravity (LOG)is an
imaginary vertical line from
the centre of gravity to the
ground or surface the
object or person.It is the
direction that gravity is
acting upon the person or
object.
• It is also known as the line
of action of the force of
gravity. In the image above you can see the line of
gravity in red going down to the ground
from the centre of gravity, indicating the
force of gravity upon the sprinter.

• The closer the line of
gravity is to the centre of
the base of support the
better balanced a person is
in this position.
• If the line of gravity fall
outside of the base of
support the person must
provide corrective muscle
action, usually a movement
otherwise they will fall.
• In the given picture in
which direction should the
player move?

• It is one thing to have a system in equilibrium; it is quite
another for it to be stable.
• If an object is in equilibrium, it is balanced, then if a force is
applied to the object it will either tilt, tip over or roll.
These three conditions are known as:
(a)stable equilibrium (it tilts and then falls
back to the original position)
(b) unstable equilibrium (it tilts and then falls
over)
(c)neutral equilibrium (it rolls)

Let us take this marble
as an example

If the body neither returns
to its original position nor
increases its
displacement further, it
will simply adopt its new
position.

If the body does not
return to its original
position but moves
further from it.

If the body returns to
its original position by
retaining the originally
vertical axis as vertical.

What I have learned about the lesson?

How balance and stability is
important in performing
activities especially in sports?

Evaluation: Identify what is asked in the following
statement.
___________1. It is an imaginary vertical line from the center of
gravity to the ground or surface the object or person.
___________2. The center of gravity of these object may be
determined by hanging and balancing it.
___________3. It is a measure of how likely it is for an object to
topple over when pushed or moved.
__________4. It defined as the horizontal stride width during the
double-support phase when both feet are in contact with the
ground.
___________5. It is your ability to control your body without
movement against gravity.

!
Closing Prayer
We thank you Lord, for allowing us to end this class successfully.
We thank you for letting us share and interact meaningfully with each other
online.
We may not be together physically but through your blessing, we were able to
learn and advance our knowledge and skills.
Grant that we continue to pursue our education despite the problems that come
our way.
May you allow us to gain more information that we could use to serve other
people.
May you send the Holy Spirit to guide us in sharing this information to the world.
We pray for the safety of the teachers, students, families, and all people in the
world.
We ask all these, in your powerful name.
Amen

The crest HIGHEST POINT
OF A WAVE.
The trough -LOWEST
POINT OF A WAVE
Amplitude- distance from
rest to crest.
The wavelength of a wave is
simply the length of one
complete wave cycle.
Parts of a Wave
a.Crest d. Amplitude
b.Trough e. Frequency
c. Wavelength
Frequency- is the number of waves that pass a point in a certain period of time.

ELECTROMAGNETIC WAVES
Chapter 5:

Radio Frequency Identification
(RFID) is a system used for
tagging and identifying
automobiles such as cars, SUVs,
trucks, and buses and works
through a small chip. This is
commonly used in the Electronic
Toll Collection(ETC).
All information are relayed
electronically via radio waves.

WiFi is another technology that
uses radio waves enable wireless
peer-to-peer connectivity and
local networks or internet
connectivity.
ELECTROMAGNETIC WAVES

• After studying electromagnetic waves for
many years, James Maxwell described
how a changing electric field produces a
magnetic field and showed that a
changing magnetic field creates an electric
field.
• Based on this assumption, Maxwell
predicted that the end result of these
interchanging fields was a train of invisible
waves of electric and magnetic fields that
could propagate even in an empty space.
These waves are the carriers of
electromagnetic energy (also known as
electromagnetic radiation).
James Clerk
Maxwell

• After Maxwell’s predictions,
electromagnetic (EM) waves were first
generated by Heinrich Hertz in 1887. They
are classified as transverse waves. The
electric and magnetic field of EM waves
are perpendicular to one another and to
the direction of the propagation.
Heinrich
Hertz

• The electromagnetic spectrum, represents the family of EM waves.
• Notice that each wave is different from the others in terms of
frequency and wavelength. However, there is one thing common to
these EM waves-they travel in the same speed, c = 3x108
m/s, in a
vacuum.

Visible light – X- ray- Radio wave– Infrared – Microwave
Longest to shorter wavelength
Radio wave – Microwave – Infrared –Visible Light – X-ray

Ultraviolet - X- ray – Microwave -Visible Light– Infrared
Highest to lowest frequency
X-ray – Ultraviolet –Visible Light –Infrared- Microwave

Visible Light – Radio wave – Ultraviolet – Gamma ray
lowest to highest energy
Radio wave – Visible Light – Ultraviolet – Gamma ray

• The EM waves in the spectrum are arranged according to frequency
and wavelength. Low frequency waves have longer wavelengths,
while high-frequency waves have shorter wavelengths.
This arrangement indicates that there is an inverse relationship
between frequency and wavelength. This relationship is also shown
in the wave equation, expressed as
c=fλ
c= speed of EM waves in meters per second(m/s)
f=frequency of EM waves in hertz (Hz or s-1
)
= wavelength of EM waves in meters (m)
λ

Sample problem 1
A tuning fork has a frequency of 310 Hz. The wavelength of the sound
produced by the tuning fork is 1.32 m. Calculate the speed of the wave.
1.
2.
• f= 310 Hz
• = 1.32 m
• c=?
c=fλ
c
3.
4. c=409.2 m/s

Sample problem 2
What is the speed of a wave with a frequency of 250 Hz
and a wavelength of .98 m?
1.
2.
• f= 250 Hz
• = .98 m
• c=?
c=fλ
c
3.
4. c=245 m/s

Sample problem 3
What is the wavelength of a wave moving at 450 m/s with
a frequency of 464 Hz?
1.
2.
• f= 464 Hz
• = ?
• c= 450 m/s
λ=
λ=
3.
4. λ =0.97 m
c
λ
f

Sample problem 4
What is the wavelength of an unidentified wave that has a wave
speed of 50 m/s and a frequency of 15 kHz?
1.
2.
• f= 15 kHz
• = ?
• c= 50 m/s
λ=
λ=
3.
4. λ =3.33x10-3
m
1kHz=1000 Hz
15000 Hz

EM waves carry energy called radiation. For this reason, EM
waves are also called electromagnetic radiation. Generally, the
higher the frequency of a wave, the more energy it carries and
the more hazard it poses. This relationship between frequency
and energy is summarized Planck's equation, expressed as
E=hf
E= energy in Joules (J) or electronvolt (eV)
( 1 eV = 1.6x10 -19
J)
h= Plancks proportionality constant between energy and
the frequency of the EM waves (h=6.63x10-34
J.s)
f = frequency in hertz (Hz or s -1
)

Sample problem 1
A photon has a frequency of 2.68 x 106
Hz. Calculate its
energy.
1.
2.
• h= 6.63 x 10-34
J.s
• f= 2.68 x 106
Hz
• E= ?
E=hf
E=(6.63 x 10-34
J.s)(2.68 x 106
Hz)
3.
4. E =1.78x10-27
J.s

Sample problem 2
•Calculate the energy of a photon of radiation with a
frequency of 8.5 x 1014
Hz.
1.
2.
• h= 6.63 x 10-34
J.s
• f= 8.5 x 1014
Hz
E= ?
E=hf
E=(6.63 x 10-34
J.s)(8.5 x 1014
Hz )
3.
4. E =5.64x10-19
J.s

Sample problem 2
•Calculate the energy (E) and wavelength () of a
photon of light with a frequency of 6.165 x 1014
Hz.
1.
2.
• h= 6.63 x 10-34
J.s
• f= 6.165 x 1014
Hz
E= ?
E=hf
E=(6.63 x 10-34
J.s)(6.165 x 1014
Hz )
3.
4. E =4.09x10-19
J.s

•Calculate the energy (E) and wavelength () of a
photon of light with a frequency of 6.165 x 1014
Hz.
1.
2.
• f= 6.165 x 1014
Hz
•  = ?
• c= 3x 108
m/s
λ=
λ =
3.
4. λ =4.87x10-7
m

•Calculate the energy and frequency of red light having a
wavelength of 6.8 x 10-7
m
• Given: wavelength of 6.8 x 10-7
m
Find: a. energy (E)
b. Frequency (f)
b. Formula: Frequency c=f(λ)
c
λ
f
(f)=
Sample problem 3

•Calculate the energy and frequency of red light having a
wavelength of 6.8 x 10-7
m
cm
Find: a. energy(E) b. Frequency(f)
b. Formula: Frequency
(f)=
Substitution (f)= =4.41x1014
Hz
Sample problem 3

• Calculate the energy and frequency of red light having a wavelength of 6.80 x 10-
5
cm
cm
• Frequency 4.41x1014
Hz
Find: a. energy (E)
b. Formula: Energy
Substitution
E=hf
E=(6.63x10-34
J.s)(4.41x1014
Hz) =2.92x10-19
J
Sample problem 3

What I have learned about
electromagnetic waves?

What are the importance of
EM waves in our daily life?

Evaluation: Solve the following problem.
1. Calculate the wavelength and energy of light that has a frequency of
1.5 x 1015
Hz.
2. Calculate the frequency of light that has a wavelength of 4.25 x 10-
9
m.
3. What is the frequency of a wave that is moving at 37 m/s with a
wavelength of .61 m?
4. What is the wavelength of a wave moving at 564 m/s with a
frequency of 750 Hz?
5. Calculate the wavelength and energy of light that has a frequency of
1.5 x 1015
Hz.

Answers:
1.  = 2.0 x 10-7
m E = 9.95 x 10-19
J
2.  = 7.1 x 1016
Hz.
3. 60. 66 Hz
4. 0.752
5.  = 2.0 x 10-7
m E = 9.95 x 10-19
J

Assignment:
1.What are the low and high frequency EM
waves?
2.Cite practical application of the different
forms of electromagnetic radiation.
3.Explain the effects of EM radiation in living
things and environment.

!
Closing Prayer
We thank you Lord, for allowing us to end this class successfully.
We thank you for letting us share and interact meaningfully with each other online.
We may not be together physically but through your blessing, we were able to
learn and advance our knowledge and skills.
Grant that we continue to pursue our education despite the problems that come
our way.
May you allow us to gain more information that we could use to serve other
people.
May you send the Holy Spirit to guide us in sharing this information to the world.
We pray for the safety of the teachers, students, families, and all people in the
world.
We ask all these, in your powerful name.
Amen

Understanding Electromagnetic Waves and propagation

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