ELECTROMAGNETIC
SPECTRUM
Week 1
OBJECTIVES:
1.Trace the development of electromagnetic wave
theory.
2.Define electromagnetic waves.
3. Describe the transmission and propagation of
electromagnetic waves.
4. Discuss the properties of EM waves.
5. Solve problems involving wavelength,
frequency, and energy of an electromagnetic wave.
6. Compare the relative wavelengths, frequencies,
and energies of the different regions of EM
waves.
What is a
wave ?
A wave can be
thought of as a
disturbance or
oscillation that
travels through
space-time,
accompanied by a
transfer of energy.
•
Kinds of waves
Kinds of waves
1. Mechanical wave
- is a wave that is
an
oscillation
of
matter
and
is
responsible for the
transfer of energy
through a medium.
Where does the energy
come from in the water
wave pictured above?
Answer:
The energy comes
from the falling
droplets of water,
which have kinetic
energy because of
their motion.
Medium
The matter through
which the wave
travels is called
the medium.
How do the
particles of the
medium move when a
wave passes through
them?
• The particles of the
medium just vibrate in
place.
•
As they vibrate, they
pass the energy of the
disturbance to the
particles next to them,
which pass the energy to
the particles next
to them, and so on.
•
Particles of the medium
don’t actually travel along
with the wave. Only the
energy of the wave travels
through the medium.
Types of Mechanical
waves
Types of Mechanical
waves
a. Transverse Wave
When the movement of
the particles is at
right angles or
perpendicular to the
motion of the
energy, then this
type of wave is
known as Transverse
wave.
Ex. light
Examples of
Transverse waves
Light
Vibrations on a
string
Ripples on the
surface of
water.
Types of Mechanical
waves
b. Longitudinal Wave
In this type of
wave, the movement
of the particle
are parallel to
the motion of the
energy
Examples of
Longitudinal waves
Sound waves
Compressions
moving along a
slinky
P-waves
Kinds of waves
2. Matter wave
- All matter exhibits a wave-like
behavior.
For example, a beam of electrons
can be diffracted just like a beam
of light or a water wave.
- The concept that matter behaves
like a wave was proposed by French
physicist Louis de Broglie
3. Electromagnetic
Wave
- considered to be
both of electric and
magnetic in nature
- contains an
electric field and a
magnetic field
3. Electromagnetic
Wave
-
All electromagnetic
waves can travel
through a vacuum at
the same speed
- do not need a medium
to travel.
Speed of light:
3.0 x 108 m/s
Characteristics
of a wave
Characteristics
of a wave
1. Amplitude
●
●
The maximum
position moved
by a point on a
wave measured
from its
equilibrium
position
The height of a
wave
Characteristics
of a wave
2. Wavelength λ
●
The distance
between two
consecutive
crest or two
consecutive
trough of a wave
Characteristics
of a wave
3. Frequency (f)
●
●
higher frequency = higher energy
The number of
waves that pass
a fixed point in
a given amount
of time
The SI unit for
wave frequency
is the hertz
(Hz)
The wave speed, frequency, and wavelength
are related by the following equation:
Where:
c=λf
c = speed of light (3.0 x 108 m/s)
f = frequency in Hertz
λ = wavelength in meters.
Sample problem 1
What is the
frequency of
the radiowave
with a
wavelength of
25 m?
Sample problem 1
What is the
frequency of
the radiowave
with a
wavelength of
25 m?
Given
c = 3 x 108 m/s
λ = 25 m
f = ?
Formula
c = f λ
λ
λ
c
λ
= f
c
or f =
λ
Sample problem 1
What is the
frequency of
the radiowave
with a
wavelength of
25 m?
Given
108
c = 3 x
λ = 25 m
f = ?
m/s
Formula
c
f =
λ
Solution
f =
3 x 108 m/s
25 m
f = 1.2 x 107 Hz
Sample problem 2
Calculate the
frequency of
a wave if the
wavelength
decreases
from 25 m to
10 m.
Sample problem 1
Calculate the
frequency of
a wave if the
wavelength
decreases
from 25 m to
10 m.
Given
c = 3 x 108 m/s
λ = 10 m
f = ?
Formula
c = f λ
λ
λ
c
λ
= f
c
or f =
λ
Sample problem 1
Calculate the
frequency of a
wave if the
wavelength
decreases from 25
m to 10 m.
Given
108
c = 3 x
λ = 10 m
f = ?
m/s
Formula
c
f =
λ
Solution
f =
3 x 108 m/s
10 m
f = 3 x 107 Hz
Sample Problem 1
λ = 25 m
Sample Problem 2
λ = 10 m
What did you observe with the wavelengths?
“The wavelength of the wave decreases”
f = 1. 2 x 107 Hz
f = 3 x 107 Hz
What did you observe with the frequencies?
“The frequency of the wave increases”
3. Kim made a wave in a spring by
pushing and pulling on one end.
The wavelength is 0.1 m, and the
wave frequency is 2 hertz. What is
the speed of the wave?
What is the relationship of
the wavelength to the
frequency?
λ
f
The wavelength is inversely proportional
to the frequency of the wave
As the wavelength decreases, the
frequency increases and vice versa
Solve the following:
1. What is the frequency of the
green light that has a wavelength
of 5.5 x 10-7m ?
2. What is the wavelength of a
microwave that has a frequency of
4.2 x 108 Hz?
3. A wave is traveling at a speed
of 2 m/s and has a frequency of 2
Hz. What is its wavelength?
Electromagnetic Spectrum
Electromagnetic Spectrum
Seatwork no. 1
1. Arrange the
following according
to decreasing
wavelength.
X-ray
Radio
wave
Gamma ray
Answer:
Radio
wave
X-ray
Gamma ray
Seatwork no. 1
2. Arrange the
following according
to increasing
wavelength.
Infrared
Microwave
Visible
light
Answer:
Visible
light
Infrared
Microwave
Seatwork no. 1
3. Arrange the
following according
to increasing
frequency.
Infrared
Microwave
Visible
light
Answer:
Microwave
Infrared
Visible
light
Seatwork no. 1
3. Arrange the
following according
to decreasing
frequency.
Ultraviolet
ray
Gamma ray
Microwave
Answer:
Gamma ray
Ultraviolet
ray
Microwave
Seatwork no. 1
3. Arrange the
following according
to decreasing
energy.
Radio
wave
Ultraviolet
ray
Infrared
Answer:
Ultraviolet
ray
Infrared
Radio
wave
1. Showed how a current
carrying wire behaves like
a magnet
a. Heinrich Hertz
2.
Showed
experimental
evidence of electromagnetic
waves and their link to
light.
b. Hans Christian
Oersted
3.
Contributed
to
developing equations that
showed the relationship of
electricity and magnetism.
c. André
Marie Ampère
4. Formulated the principle
behind
electromagnetic
induction
d. James Maxwell
5.
Demonstrated
the
magnetic effect based on
the direction of current
e. Michael Faraday
Seat Work
no. 1
https://www.du
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ience/quiz/wav
es_questions.p
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II. Solve the following:
1) A wave has frequency
of 50 Hz and a wavelength
of 10 m. What is the
speed of the wave?
2) The speed of a wave is 65
m/sec. If the wavelength of
the wave is 0.8 meters, what
is the frequency of the wave?
I.
1. Arrange the
following according
to increasing
energy.
microwave
X-ray
Ultraviolet
ray
Answer:
microwave
Ultraviolet
ray
X-ray
Seatwork no. 1
2. Arrange the
following according
to increasing
wavelength.
microwave
infrared
Gamma ray
Answer:
Gamma ray
infrared
microwave
Seatwork no. 1
3. Arrange the
following according
to decreasing
wavelength.
Ultraviolet
ray
Visible
light
Gamma ray
Answer:
Visible
light
Ultraviolet
ray
Gamma ray
Photons
- are bundles of wave
energy.
The energy of a photon
is given by the
equation:
E=hf
Where:
E= Energy
h= Planck’s Constant
(6.63 x 10-34 joules
second)
f= frequency of the EM
wave
Example Problems:
(Assume that the
waves propagate in a
vacuum.)
1. A photon has a
frequency (f) of
2.68 x 106 Hz.
Calculate its energy
2. Calculate the
energy (E) of a
photon of light with
a frequency (f) of
6.165 x 1014 Hz.
Seatworks:
Answer: WHAT TO DO
(PROCEDURE) PART B.
SOLVING PROBLEMS
INVOLVING WAVELENGTH,
FREQUENCY, AND ENERGY
OF AN ELECTROMAGNETIC
WAVE.