SCIENCE
QUARTER 2 : REVIEWER
ELECTROMAGNETIC WAVES
●​ It is both electric and magnetic in
nature; in other words, it has an
electric field and a magnetic field
●​ An electromagnetic wave is
produced by a charge that changes
it's direction or speed
●​ Electrons are charged particles that
can produce both electric and
magnetic field
PROPERTIES OF E.M. WAVES
1. Produced by accelerated or oscillating
charge
2. They do not require medium for
propagation
3. They travel free in space with a speed of
3x10⁸ m/s
PRINCIPLES OF E.M. WAVES THEORY
1.​ Many natural phenomena exhibit
wave-like behaviors. All of
them—water waves, earthquake
●​ An electron moves back and forth in
order to create an electromagnetic
field
waves, and sound waves—require a
medium to propagate. These are
examples of mechanical waves.
●​ Electromagnetic waves are also
considered transverse waves, which
means that both electric and
magnetic waves oscillate
perpendicularly to each other.
●​ It travels at a speed of 3x10⁸ m/s or
300,000,000 m/s and is denoted as
C, the speed of light
●​ Nothing is faster than the speed of
light. Electromagnetic waves and the
speed of light are equal
●​ Wavelength ↓ = Frequency ↑
Wavelength ↑ = Frequency ↓
Inversely Proportional
2.​ Light can also be described as a
wave—a wave of changing electric
and magnetic fields that propagate
outward from their sources. These
waves, however, do not require a
medium to propagate.
3.​ They propagate at 300,000,000
meters per second through a
vacuum.
4.​ Electromagnetic waves are
Heinrich Hertz (1887)
transverse waves. In simpler terms,
↪ He was able to perform many
the changing electric and magnetic
experiments that helped explain reflection,
fields oscillate perpendicular to each
refraction, polarization, interference, and
other and to the direction of the
velocity of electric waves. The hertz, the SI
propagating waves. These changing
unit of frequency, is named after him.
electric and magnetic fields generate
each other through Faraday's Law of
Albert Einstein (1905)
Induction and Ampere's Law of
↪ He formulated the photoelectric effect.
Electromagnetism. These changing
fields dissociate from the oscillating
Wilhelm Gilbert (1603)
charge and propagate out into space
↪ He discovered that Earth was magnetic
at the speed of light.
and theorized that electricity and magnetism
are not the same. The gilbert, a unit of
5.​ When the oscillating charge
magnetic potential, was named after him.
accelerates, the moving charge's
electric fields change, too
James Clerk Maxwell (1861)
↪ He described how electric charges and
❝ Electromagnetic waves are ordered
electric currents act as sources of electric
or arranged by frequency, also known
and magnetic fields that form the basis of
as electromagnetic spectrum. ❞
the electrical field of science and
technology.
HISTORICAL ANTECEDENT OF
ELECTROMAGNETIC WAVES
Wilhelm Eduard Weber (1856)
↪ He discovered that the ratio of
Joseph Henry (1831)
electrostatic to electromagnetic units equals
↪ He was the first to discover
the value of the speed of light, leading to the
electromagnetic induction, the production of
conjecture that light is an electromagnetic
an electric current across a conductor
wave. The weber, named after him, is the SI
moving through a magnetic field. The SI unit
unit of magnetic flux.
of inductance, the henry, was named after
him. 1831
Hans Christian Oersted (1820)
↪ This is used to provide local radio
↪ He discovered that an electric field that
communication coverage such as
flows through a wire creates a circular
AM, FM, and television
magnetic field. The Oersted, a unit of
broadcasting.
magnetic intensity, is named after him.
↪ This can be used for one-way
communication from the military to
↪ He proved his discovery by showing that
submerged submarines as they
moving electrons can create a magnetic
penetrate to a significant depth into
field.
seawater.
Charles-Augustin De Coulomb (1785)
●​ Sky Wave Propagation
↪ Developed Coulomb's Law, which defined
↪ Is also known as Ionosphere
the electrostatic force of attraction and
Wave propagation.
repulsion. The coulomb, the SI unit of
charge, was named after him.
↪ It refers to radio wave propagation
via ionosphere.
METHODS OF PROPAGATION
↪ This happens when
●​ Ground Wave Propagation
electromagnetic waves travel
↪ Is also known as Surface Wave
towards the sky after propagation
propagation.
and reflect to the earth from the
ionosphere.
↪ It is a method of radiofrequency
propagation that uses the area of the
↪ This is the simplest mode of
earth and the ionosphere for
propagation and provides
transmission that can propagate at
continuous support in
frequencies below 3 MHz.
communications.
↪ This happens when the
↪ An electromagnetic wave directed
electromagnetic waves propagate
upward at some angle from the
and travel along the surface of the
earth’s surface is called skywaves.
earth towards the receiver antenna.
●​ Space Wave Propagation
c=λf
↪ Is also known as Tropospheric
Where :
Wave propagation.
c = Wave speed (m/s)
f = Frequency (Hz)
↪ It can travel directly or after
λ = Wavelength (m)
reflecting from the earth’s surface to
the troposphere surface from the
↪ Since all the EM waves have the same
transmitter antenna to the receiver
speed which is equal to the speed of light,
antenna.
as wavelength decreases, the frequency of
the wave increases.
↪ This happens when the
electromagnetic waves are
↪ Every type of EM wave carries a specific
propagated from the transmitter
amount of Energy (E), the discovery of
antenna and it travels in a straight
which was made possible by a scientist
line without any reflection or
named Max Planck. He was able to
refraction.
calculate the exact multiplier to get the
energy of a photon carried by an
↪ This is utilized in television and
Electromagnetic wave. It is called Planck’s
radar communications.
Constant with a value of 6.63 x 10−34 J.s
(Joules second). The constant value can be
SOLVING F.E.W COMPARISON
used to get the energy of an EM wave using
this formula:
↪ All electromagnetic waves can travel
through a medium but unlike other types of
E=hf
waves, they can also travel in a vacuum
Where :
(empty space).
E = Wave energy (J)
h = Planck’s Constant (J.s)
↪ They travel in a vacuum at a speed of 3.0
f = Frequency (Hz)
x 108 m/s and denoted as c, the speed of
light. The wave’s speed, frequency, and
↪ Combining Formula number 1 and 2 can
wavelength are related by the following
give you the equation below that you may
equation:
also use in computing wave energy:
E=hc/λ
ELECTROMAGNETIC WAVE
SPECTRUM
↪ Divided into regions based on the
frequency or wavelength interval
↪ Electromagnetic waves are categorized
according to their frequency or equivalently
according to their wavelength
PRACTICAL APPLICATIONS OF EM
WAVES
↪ Visible light has a wavelength from
~400nm to ~700nm
↪ Violet light has a frequency of ~7.5
Radio Waves
↪ Are part of the E.M. spectrum, it has the
longest wavelength and carries the lowest
energy and frequency.
x 1014 Hz and a wavelength
of ~400nm
↪ Produced by vibrating electric current in
an antenna and is widely used for wireless
communication.
↪ Red light has a frequency of
~4.3 x 1014 Hz and a wavelength of
~700nm
●​ Waves of shorter wavelength
and higher frequency :
↳ Ultraviolet
↳ X-Rays
↳ Gamma Rays
●​ Waves of longer wavelength
and lower frequency :
↳ Infrared Light
↪ Bends around buildings and hills by
diffraction.
Components of Radio Waves
↪ Transmitter
↪ Antenna
↪ Receiver
Microwaves
↪ It is produced by a magnetron. It can
penetrate through the atmosphere, that's
why it is best used if the broadcast is live via
satellite.
↪It is good in sending signals to a specific
receiver (point-to-point communication)
↳Microwaves
↳ Radio and television waves
↪ For cooking, microwaves are used by
heating up the water molecules from food.
Infrared Radiation
↪ Is the type of EM waves that is most often
associated with heat.
↪ All objects emit infrared
↪ Our bodies radiate infrared and the color
of infrared radiation depends on the
temperature of the body part emitting the
wave that is why under infrared camera or
night goggles our image appears colorful.
↪ Sir William Heschel was credited for the
discovery of Infrared Radiation (IR)
↪ Infrared means below red
Kinds of UV
UVA - accounts for almost 95% of
the solar UV reaching the surface of
the Earth.
UVB - is mostly filtered by the ozone
in the atmosphere.
UVC - almost completely absorbed
by the atmosphere and no longer
reaches the Earth’s surface.
X - Rays
↪ They can pass through our bodies and
are used in medical imaging, like x-ray
machines to see our bones and organs
Visible Light
↪ This is the type of electromagnetic wave
that allows us to see the world around us.
Visible light comes in different colors like
red, orange, yellow, green, blue, indigo,
violet. Each color has different wavelengths.
↪The discovery of X-rays was credited to
Wilhelm Conrad Roentgen. That is why
these rays are sometimes called Roentgen
rays.
↪ Also known as white light
↪ Roentgen named the rays he discovered
X-rays because he did not know their nature
or origin.
Ultraviolet Radiation
↪ It comes from the sun and is responsible
for causing sunburns. We can’t see UV
radiation but it can be harmful to our skin
and eyes.
↪ It has higher frequency than the violet part
of visible light that’s why ultraviolet means
beyond violet.
↪ Discovered by German physicist John
Wilhelm Ritter
Types of X-Rays
Soft X-Rays - penetrate soft
substances such as flesh and
bones.
Hard X-Rays - are more penetrating
as compared with soft x-rays and
are mainly used in industries.
Medical Use of X-Rays
X-ray radiography is used to detect
bone fractures, tumors, etc.
Mammography is used to detect and
diagnose breast cancer.
Gamma Radiation
↪ Has the shortest wavelength and has the
higher frequency of all the radiation
↪ Produced by nuclear reactions and can
be very harmful
↪ Scientists uses gamma rays to treat
cancer
Fiber Optic Cables
↪ transmit data faster as they can carry
higher frequency ranges. At higher
frequencies, copper cables lose signal
strength. Because of this, fiber optic cables
also have greater bandwidth than copper
cables of the same diameter.
↪ do not carry electric current making them
less susceptible to electromagnetic
interference that interrupts data
transmission.
↪ can carry signals farther than copper
cables.
↪ are lighter and thinner making them less
prone to damage.
NON-IONIZING E.M RADIATIONS
↪ Non-ionizing radiation is a series of
energy waves composed of oscillating
electric and magnetic fields traveling at the
speed of light.
↪ Includes radio wave, microwave, infrared
and visible light. These E.M. waves are of
low energy level and are not known to
cause harmful effects to living organisms.
↪ The E.M. Wave radiation from Microwave
ovens, global positioning systems (GPS),
Cellphones, TV stations, FM and AM radio,
Computers and other gadgets are all
examples of non-ionizing radiation.
↪ Low-frequency Ultraviolet radiation can
still be considered as Non-ionizing radiation
but at certain amounts, could pose hazards
to our health such as causing sunburns and
even skin cancer.
IONIZING E.M. RADIATIONS
↪ is a type of energy that is released in the
form of electromagnetic waves. It can be
observed depending on the energy that
electromagnetic waves emit.
↪ includes high frequency UV radiation,
X-Ray, and Gamma Ray.
↪ Ionization is the process by which an
atom or a molecule acquires a negative or
positive charge by gaining or losing
electrons, often in conjunction with other
chemical changes.
↪ Ionization radiation causes changes in the
structure of atoms and molecules by
ionization, so that’s why ionizing radiation
can cause damage to living atoms or
molecules and have the tendency to cause
changes in the structure of DNA in the living
organism.
FACTORS TO CONSIDER IN
MINIMIZING E.M. WAVES RADIATION
EXPOSURE
Distance
↪ As the distance from the source of
radiation increases, the risk of
exposure becomes less.
TIME
↪ As the time of exposure increases,
the risk of getting harmful effects
also increases. Being exposed to
sources of E.M.Radiation for
prolonged periods of time could
produce harm to the human body.
SHIELDING
↪ Radiation can be absorbed by
materials placed between the source
of the radiation and the user. The
type of shielding that is the most
appropriate to use depends on the
nature of the penetrating power of
the radiation. Materials such as
aluminum and lead are better in
shielding against radiation.
RADIATION PROTECTION
PRINCIPLES
Justification
↪ means that any exposure produces
sufficient benefit to offset the radiation harm
that it might cause. Thus, if the exposure
has no benefit, it is not justified.
Dose Limitation
↪ The normal exposure of individuals shall
be restricted so that neither the total
effective dose nor the total equivalent dose
to relevant organs or tissues, caused by the
possible combination of exposures from
authorized practices, exceeds any relevant
dose limit, except in special circumstances.
Optimization of Protection
↪ can be attained by keeping exposure As
Low As Reasonably Achievable (ALARA) or
As Low as Reasonably Practicable –
residual risks should be made as low as
possible and this can be achieved by
making sure that the cost involved in
reducing the risk further would be grossly
disproportionate to the benefit gained
EFFECTS OF RADIATION IN VARIOUS
UNITS
Exposure
↪ The amount of radiation traveling through
the air is measured in roentgen (R).
Absorbed dose
↪ describes the amount of radiation
absorbed by an object or person. The unit
for absorbed dose is the gray (Gy). One
gray is equal to 100 rads.
Effective dose
↪ describes the amount of radiation
absorbed by a person, adjusted to account
for the type of radiation received and the
effect on human organs.
↪ The unit used for effective dose is sievert
(Sv) or rem, wherein 1 Sv = 100 rems.
↪ On the average the annual acceptable
limit for radiation should not exceed 5 rems.
Radioactivity
↪ The spontaneous disintegration of atoms
and the excess energy emitted is a form of
ionizing radiation.
↪ Unstable elements which disintegrate and
emit ionizing radiation are called
radionuclides. Expressed in becquerel (Bq)
MIRRORS AND LENS
Plane Mirrors
↪ Will always result to the same image
regardless of the objects’ location
Reflection of Light
↪ When a ray of light falls on any object
(polished, smooth, shiny object), light from
the object bounces back those rays of light
to our eyes, and this phenomenon is known
as reflection or reflection of light.
Law of Reflection
↪ The diagram to the left shows how the
incident ray is reflected back as a reflected
ray.
↪ The angle of incidence is equal to the
angle of reflection (θi = θr); and the incident
ray, the normal and the reflected ray, all lie
in the same plane.
CHARACTERISTICS OF IMAGES
FORMED
●​ Image
↪ Real (when rays converge)
↪ Virtual (when rays diverge)
●​ Orientation
↪ Upright
↪ Inverted (can be lateral)
●​ Location
↪ Depends on the object's location
●​ Size
↪ Magnification
↳ Larger (>1)
↳ Smaller (<1)
↳ Same / Equal (1)
CURVED MIRRORS
↪ Are mirrors with curved reflecting surfaces
which may be convex or concave.
●​ Concave Mirror
↪ is also known as a converging
mirror since in this type of mirror
light rays converge at a point after
they strike and are reflected from the
reflecting surface of the concave
mirror.
↪ In the majority of the cases, a
concave mirror produces real and
inverted images except when the
object is placed very near to the
mirror i.e. pole (p) and the focus (f)
where the image produced is virtual
and erect.
●​ Convex Mirror
↪ is also known as a diverging mirror
since here light rays diverge after it
strikes the reflecting surface of the
convex mirror.
↪ Convex mirrors always form a
virtual, erect, and smaller image.
CURVED MIRRORS
❝ The reflection of curved mirrors
depends on the location of the object. ❞
PARTS OF CURVED MIRRORS
Concave Mirror
Scenario 1 - Object located beyond C :
Image : Real
Orientation : Inverted
Location : Between C and F
Size : Smaller (<1)
Scenario 4 - Object located at F :
All : None
❝ Parallel light rays do not intersect therefore no
image is formed.❞
Scenario 5 - Object in front of F :
Scenario 2 - Object located at C :
Image : Real
Orientation : Inverted
Location : At the object
Size : Same (1)
Image : Virtual
Orientation : Upright
Location : Opposite side of the mirror
Size : Larger (>1)
Convex Mirror
One Possible Scenario :
Scenario 3 - Object between C and F :
Image : Real
Orientation : Inverted
Location : Beyond the object
Size : Larger (>1)
Image : Virtual
Orientation : Upright
Location : Opposite side of mirror
Size : Smaller (<1)
MIRROR EQUATION
↪ expresses the quantitative relationship
between the object distance (do), the image
distance (di), and the focal length (f).It is
express as
PARTS OF CONVEX LENS
1/f = 1/do + 1/di
MAGNIFICATION EQUATION
↪ relates the ratio of the image distance and
objects’ distance to the ratio of the image
height (hi) and object height (ho). It can be is
written as
Convex Lens
Scenario 1 - Object located beyond 2F :
m = hi / ho = -di / do
Sign Conversion
↪ The sign conventions for the given
quantities in the mirror equation and
magnification equations are as follows:
f is + if the mirror is concave
f is - if the mirror is convex
di is + if the image is real; located in front
di is - if the image is virtual; located behind
hi is + if the image is upright
hi is - if the image is inverted
Image : Real
Orientation : Inverted
Location : Between F and 2F on the other side
Size : Smaller (<1)
Scenario 2 - Object located at 2F :
CURVED LENSES
●​ Convex Lens
↪ Converges rays of light that are
traveling
↪ Thick across their middle and thin
at their upper and lower edges
●​ Concave Lens
↪ Diverges rays of light that are
traveling
↪ Thin across their middle and thick
at their upper and lower edges
Image : Real
Orientation : Inverted
Location : At 2F on the other side
Size : Same (1)
Scenario 3 - Object in front of 2F :
Image : Real
Orientation : Inverted
Location : Beyond 2F on the other side
Size : Larger (>1)
PARTS OF CONCAVE LENS
Concave Lens
One Possible Scenario :
Scenario 4 - Object located at F :
Image : Virtual
Orientation : Upright
All : None
❝ Parallel light rays do not intersect therefore no
image is formed.❞
Scenario 5 - Object in front of F :
Location : Somewhere on the same side; behind the object
Size : Smaller (<1)
LENS EQUATION
↪ expresses the quantitative relationship
between the object distance (do), the image
distance (di), and the focal length (f).It is
express as
1/f = 1/do + 1/di
Image : Virtual
Orientation : Upright
Location : Somewhere on the same side; behind the object
Size : Larger (>1)
MAGNIFICATION EQUATION
↪ relates the ratio of the image distance and
objects’ distance to the ratio of the image
height (hi) and object height (ho). It can be is
written as
m = hi / ho = -di / do
Sign Conversion
↪ The sign conventions for the given
quantities in the mirror equation and
magnification equations are as follows:
f is + if the mirror is double convex
f is - if the mirror is double concave
di is + if the image is real; located in front
di is - if the image is virtual; located behind
hi is + if the image is upright
hi is - if the image is inverted
SUMMARY OF MIRRORS AND
LENSES
↪ Image characteristics in concave mirrors
depend on the object’s location.
↪ Image characteristics in convex mirrors
will produce the same image regardless of
the object's location.
↪ Image characteristics in convex lenses
depend on the object’s location.
↪ Image characteristics in concave lenses
will produce the same image regardless of
the object's location.
MIRRORS AND LENSES AND THEIR
USE IN OPTICAL INSTRUMENTS
Reflection
↪ refers to the bouncing back of light when
it hits a smooth surface.
Refraction
↪ is the bending of light when it travels from
one medium to another.
●​ Microscope
↪ is an optical instrument that is
composed of two convex lenses of
short focal length. These are
objective lens and eyepiece lens.
↪ The object is placed near the focal
point of the first objective lens that
forms the first image. This object is
formed between the eyepiece lens
and its focus.
↪ Also, this image becomes the
object of the eyepiece lens. Then the
eyepiece lens forms the final image
that is virtual and larger.
●​ Camera
↪ Is an optical instrument that forms
and even records an image of an
object.
↪ The image may be recorded on
film or it may be detected by an
electronic sensor that stores the
image digitally.
↪ The camera uses a lens and when
the light passes through it, it forms a
reduced real image.
●​ Telescope
↪ a tubular optical instrument for
viewing distant objects through
reflection or refraction of light rays
through a lens.
Refracting Telescope
↪ use lenses to bend the light to a
specific focal point. The basic
refracting telescope has two lenses.
↪ The first lens is called the
objective lens. This lens is a convex
lens that bends the incoming light
rays to a focal point within the
telescope.
↪ The second lens is called the
eyepiece. This lens takes the light
from the focal point and spreads it
out across the retina of your eye.
Reflecting Telescope
↪ use mirrors instead of lenses to
focus the light. A concave mirror is
used to gather light and reflect it to a
focal point. To get the light out of the
telescope, another mirror is used to
direct the light to an eyepiece.
●​ Binoculars
↪ is an optical instrument
consisting of two similar
telescopes, used for
providing a magnified view of
distant objects.
↪ The objective lens takes in
light and captures an image.
↪ The second lens, the
eyepiece lens, magnifies the
image so that it’s clearer for
your eye. The eyepiece lens
can be thought of as a
magnifying glass, expanding
the small image it picks up
into a larger one for you to
view.
↪ Each set of binoculars has
a total of 4 prisms.
Prism
↪ are essentially just large
wedges of glass that rotate
and reflect the image. It
needs two prisms to rotate
the image to 180 degrees,
each prism effectively
rotating the image 90
degrees.
ELECTROMAGNETISM AND
ELECTROMAGNETIC INDUCTION
Hans Christian Oersted (1820)
↪ discovered that a current-carrying wire
produces a magnetic field.
↪ His discovery led to the creation of
electromagnets. An electromagnet is a coil
of wire that uses an electric current to
produce a magnetic field.
↪ Electromagnets are used in televisions,
radios, cell phones, speakers, data storage
devices, microphones, and doorbells.
Michael Faraday (1831)
↪ discovered that electric current is
generated in an electric conductor by
moving or changing the magnetic field
surrounding it.
↪ This process is called electromagnetic
induction. A current produced by a magnetic
field in electromagnetic induction is an
induced (or produced) current.
↪ Electromagnetic induction is summarized
by Faraday's law, which states that: “The
induced voltage in a coil is proportional to
the product of the number of loops and the
rate at which the magnetic field changes
within those loops.”
ELECTRIC GENERATOR AND
ELECTRIC MOTOR
Electric motor
↪ is a device that converts electrical energy
into mechanical energy using the magnetic
turning effect on a coil.
Parts and functions :
• Source is either battery or an electrical
outlet
• A commutator is a metal ring that is
divided into two separate halves. It is
attached to the coiled wire.
• The armature is a loop or coil of wire in
which electricity passes through after
leaving the commutator. The armature is
surrounded by magnets.
• The magnets supply the magnetic field
that causes the armature to rotate as
electricity passes through it.
How does it work?
↪ As electricity passes through the
commutator, it goes to the armature that is
surrounded by a magnetic field. The
armature rotates to oppose the magnetic
field. The magnetic force produces a turning
force that rotates the armature. Since the
commutator is divided into half, it reverses
the electric current – each half rotation – to
keep the turning force in the same direction.
This process is repeated many times each
second. The electric motor operates on the
principle of electromagnetism.
Electric generator
↪ converts mechanical energy into electrical
energy usually by rotating a coil within a
magnetic field.
↪ The parts of the electric motors and
electric generators are almost the same.
They only differ in the way they transform
energy.
How does it work?
↪ An electric generator operates on the
principles of electromagnetic induction. It
produces an electric current by spinning a
coil within a stationary magnetic field. This
happens because when the coil of wire
rotates, it cuts the magnetic lines of forces
between the two magnets surrounding it.
This event induced electricity. When the coil
is placed parallel to the magnetic lines of
force, no lines of force are cut, thus, no
electricity is produced.
common sense lang ‘to