Science Reviewer Electromagnetic Spectrum

❖ NON-IONIZING is low frequency and dangerous to our cell to absorbed

• Wave (radio waves, microwaves, infrared and visible waves)
❖ The movement up and down or back and forth ❖ IONIZING (Ultraviolet, x-rays and gamma rays)
❖ One of a series of ridges that moves across the surface of a ❖ EM Waves have an electric and Magnetic field
liquid. ❖ Ems are transverse waves. Electric and magnetic fields oscillate in a plane
that is perpendicular to the propagation of the waves
3 types of waves:

❖ Mechanical waves BRIEF HISTORY OF THE ELECTROMAGNETIC THEORY

❖ Moves through the medium (solid, liquid and gas) ❖ Hans Christian Oersted Danish Physicist Discovered incidentally,
❖ Electromagnetic waves 1820- magnetic needle is deflected when the current in a nearby wire.
❖ Do not require medium to move Relationship b/w electricity and magnetism.
❖ Matter Waves ❖ Andre- Marie Ampere - Experiment designed to elucidate the exact
nature of the relationship b/w electric current- flow and magnetism, as well as the
❖ Electrons and particles
relationships governing the behavior of the electric currents in various types of
conductors.
❖ AMPERE’S LAW (law of electromagnetism) mathematically the magnetic
force between 2 electrical currents.
❖ Michael Faraday 1821- ELECTROMAGNETIC INDUCTION- electrical
current from a changing magnetic field. - took the work of Oersted and Ampere
in the magnetic properties of electrical currents. - When electrical current
passed through the coil another very short current generated in a nearby coil. -
Progress not only of science but also in society. - Used today to generate
electricity on a large-scale power station.
❖ Joseph Henry (1829) • improvements by insulating the wire instead of
Characteristics of Wave the iron core. • He was able to wrap many turns of twire around the core thus
• Amplitude – measure greatly increase the power of the magnet. • Electromagnet that could support
• Crest – top • Trough – bottom 2 063 pounds a world record at the time. • Searched for electromagnetic
• Rarefaction – separation of waves induction in 1831. • 1st to notice the principle of self- induction.
• Compression – compressed of waves ❖JAMES CLERK MAXWELL – - - Physicist and mathematician proposed
• Period (s)– time it takes a certain crest or trough to travel a distance of Faraday's electromagnetic induction to happen in the empty space. •
one wavelength
Symmetry between the fields fascinated him so much. • Added two basic
• Frequency (1/s)(hz) – number of crest
Principles of electromagnetism: (1) A changing electric field in space produces a
• Wavelength – distance of any two successive crest, troughs, rarefaction or
magnetic field (2) A changing magnetic field in space produces electric field. •
compressions
Proposed that the alteration of electric and magnetic fields, generating and
• The amount of energy in a wave is related to its amplitude and its frequency.
propelling each other in space, can be thought of as a form of moving energy.
• Largest Amplitude = Least Powerful wave
❖ Heinrich Hertz
• Smallest Amplitude = Most Powerful wave
• It was only after the death of Maxwell which a German physicist, Heinrich
 Hertz, designed an experimental set up that was electrical in nature and able to ❖ MICROWAVES
generate and detect electromagnetic waves. - Have higher
frequency!
ELECTRIC AND MAGNETIC FIELDS TOGETHER - Ground
• A changing magnetic field produces an electric field. equipment is
• A changing electric field produces a magnetic field. used to transmit
• Both the electric field and the magnetic field oscillate perpendicular to each signals to a
other and to the direction of the propagating wave. satellite that will
amplify that
EXPLORING THE ELECTROMAGNETIC SPECTRUM signal and will
• The electromagnetic (EM) spectrum is a continuum of electromagnetic return it to the Earth to be received by another ground
waves arranged according to frequency and wavelength. It is a gradual equipment.
progression from the waves of lowest frequencies to the waves of highest - Used to transmit signals overseas.
frequencies.
• According to increasing frequency, the EM spectrum includes: ❖ Radar (Radio Detection and Ranging)
- Radio waves - Used to locate, track, recognize or detect object
within range.
- Microwaves
- Infrared
- Commonly used in national defense by tracking
aircrafts
- Visible light
- Determine the speed of automotive vehicles.
- Ultraviolet
- tv and radio
- X- rays
- Gamma rays • Mobile phone
• The gamma rays have photons of high energies while radio waves - Works by transmitting microwaves which are received by
have photons with the lowest energies. cell sites and delivered to a target mobile phone.
• Microwave Oven
- Used to cook or heat food.
PRACTICAL APPLICATIONS OF THE DIFFERENT REGIONS OF EM - The water molecules of the food inside start to vibrate—
WAVES production of intermolecular friction between the
- Have the longest wavelengths and the lowest frequencies molecules of the food.
- Can produce by making electricity oscillate in an aerial, or antenna, and
are used to transmit sound and picture information over long ❖ INFRARED
distances. - Lie in the region beyond the red end of visible spectrum!
- The wavelength is too long to be visible in the naked eye.
The broadcaster uses a Microphone • Infrared radiation is most noticeable in hot
Microphone- Converts the sound waves to audio objects.
frequency signals (electrical signal) and acts as receptor. (USES OF INFRARED)
 1. Photographs taken from a satellite. - It helps our body to produce Vitamin D which is essential in our
2. Shows the body temperature, medical diagnosis. body’s calcium absorption.
- Medical Diagnostic Thermography - Too much exposure may lead to aging/damage of DNA in skin
3. Remote controls cells or worst to skin cancer.
4. Night vision goggles. • UV lamps
5. Autofocus cameras. - Used in checking signature on passbook, it can determine if the
money is real.
❖ VISIBLE LIGHT • Sterilizing water from drinking fountains
- Shortest waves present can be detected by the eye. - In Japan, UV rays are used to disinfect their toilets.
(Light waves)
- When light passes through a prism, it is separated into its
❖ X-RAYS
constituent colors: red, orange, yellow, green, blue,
- Have short wavelengths and high frequencies and
indigo and violet
are very penetrating.
- Violet has the shortest wavelength and red has the
- Produced by rapid acceleration of electrons in X-ray
longest.
machines that collide with atoms, the atoms emit X-rays
• Phototherapy
- Used in photography to help doctors look inside the body
Use of light in medical treatment of a variety of ailments and help them in diagnosing bone fractures and tumors.
from topical infections and chronic wounds to - USED Medical equipment needs to be sterilized before
autoimmune and chronic degenerative diseases. using.
- Specialist who is conducting studies about phototherapy • Short wavelength X-rays can penetrate even
- His team focuses on wavelegths of light that lie in two regions: through metals.
longer wavelengths in the far-red to near-infrared (NIR) region - Can damage living cells, can damage body tissues, and
and shorter wavelegths in the visible blue region of the can cause cancer.
spectrum.
• Fiber optics/ Optical Fibers ❖ GAMMA RAY
- Long, thin strands about the diameter of a human hair drawn - High energy waves produced from nuclear reactions.
glass. - Have shorter wavelengths than X- rays.
- Transmission medium- a “pipe” to carry signals over long distances - More dangerous than x-rays because of radioactive
at very high speeds. substances
- Was used by doctors to see the patients inside body without - They can kill living cells that is why they are used to treat
conducting a major surgery. cancer through a process called radio therapy.
- Used for sterilization of medical equipment.
❖ ULTRAVIOLET
- Invisible radiation that lies beyond the violet end of the visible CHARACTERISTICS OF IMAGES FORMED BY MIRRORS
spectrum.
- Has a shorter wavelength that violet light and carry more energy. A mirror is a smooth reflecting surface, usually made of polished metal or
glass that has been coated with metallic substances.
- Best known to come from the sun.
REFLECTION OF LIGHT • Size depends on the mirror used.
Incident Ray - the ray if light approaching the mirror represented by an
arrow. TYPES OF MIRRORS
Reflected Ray - the ray of light which leaves the mirror and is represented PLANE MIRROR
by an arrow pointing away from the mirror. • Reflecting surface is a flat surface.
Normal Line - an imaginary line that can be drawn perpendicular to the • Virtual and upright
optical element. • Equal size of the object.
CURVED/spherical MIRROR
LAW REFLECTION OF LIGHT - Reflecting surface is a section of sphere.
❖ Incident ray reflected ray and normal line on the same plane. KINDS OF CURVED/spherical MIRROR
❖ Angle of incidence is equal to angle of reflection.
CONVEX MIRROR

TYPES OF REFLECTION OF LIGHT - Reflective surface bulges towards the light surface
called Diverging Mirror because parallel incident rays
Specular/Regular Reflection diverge after reflection. When extending the reflected
rays behind the mirror, the rays converge at the focus
- Smooth and polished Surface
behind the mirror.
- Produce clear and sharp reflection of light. - Regardless of the
position of an object,
Diffused/Irregular Reflection image is smaller.
- Rough Surface - Virtual and upright

CONCAVE MIRROR
REFRACTION OF LIGHT
- reflective surface
- The change in direction of a wave passing from one medium to bulges away from the
another or from a gradual change in the medium. light source.
TYPES OF IMAGES - called
Converging Mirror
REAL because the parallel
• Inverted incident rays
• Formed in front of the mirror. converge or
• Size depends on the location of the object with respect to the mirror. meet/intersect at a
focal point after
VIRTUAL reflection.
• Upright
• Formed at the back of the mirror.
 THE SIGN CONVENTIONS FOR MIRROR no image formed.
As the object moves closer to the lens, the image becomes larger
f is positive (+) if the mirror is a concave and farther.
mirror
f is negative (-) if the mirror is a convex
mirror DIFFERENCE OF MIRROR AND LENSES
q is (+) if the image is a real image and located on
MIRROR
the object's side of the mirror.
q is (-) if the image is a virtual image and located Has one focal point
behind the mirror. Exhibits reflection of light
h' is (+) if the image is an upright image.
h' is (-) if the image is an inverted image. LENS

Has two focal points

Exhibits refraction of light
QUALITATIVE CHARACTERISTICS OF IMAGES FORMED BY LENSES

LENSES

- AN OPTICAL DEVICE WHICH IS MADE OF TRANSPARENT

MATERIAL WHICH BENDS LIGHT

TYPES OF LENSES

CONCAVE LENS

Diverging lens
Thicker at the edge than the middle
Virtual, larger and upright

CONVEX LENS

Converging lens
Thicker at the middle than the edge HISTORY OF MAGNETS:
magnifying glasses
 • The word “MAGNET” originated from certain stones discovered by the and becomes magnetized with the opposite polarity as the magnet.
Greeks more than 2000 yrs. Ago in the island of Magnesia.
• Those hard block stones called Lodestones had an unusual feature in • Imagine you have a bar magnet and a variety of objects, including
which they can attract pieces of iron. another magnet, a paperclip, a wooden block, and a nail. Based on
• Today this stone is known as magnetite, magnetized ore of iron. your understanding of magnetism, The bar magnet will attract the
Key Concepts : other magnet depending on their polarities, but will not attract the

• Magnets exert either a force of repulsion or attraction. paperclip, wooden block, or nail.

• If a force of repulsion only is possible between an object and a magnet, then

the object interacting with the magnet may also be a permanent magnet or a
temporarily magnetized ferromagnetic material

• If a force of attraction only is possible between an object and a

magnet, then the object interacting with the magnet contains a
ferromagnetic substance and is considered naturally magnetic.

• Magnetic Field
The area around a magnet in which the effect of magnetism is felt. We use the
magnetic field as a tool to describe how the magnetic force is distributed in the
space around it.
• Magnetism
• the force exerted by magnets when they attract or repel other
objects or each other.
• Induced Magnetism
When a non-magnetic iron is placed near a magnet it gets magnetized, for example,
an iron nail that possesses no magnetism will get it’s own magnetic field if a
magnet gets near it or touches it.
• Lodestone

- has the property of attracting iron particles to it.

• Ferromagnetic
materials which exhibit a spontaneous net magnetization at the atomic level, even
when no external magnetic field is present. However, when placed near a
magnetized material it will inherit the magnetic field that is present in said
magnetized material.

• An unmagnetized iron nail is brought close to a strong permanent

magnet, The nail experiences an attractive force from the magnet