Transcript The Electromagnetic Spectrum - Warren Hills Regional School District

What are Electromagnetic Waves?
Electromagnetic waves are transverse
waves produced by the motion of
electrically- charged particles.
Interesting Thing That Electrically Charged Do
CHARGED PARTICLES CAN DO SOME NEAT TRICKS:
Aurora Borealis - When electrically charged particles are ejected from the
Sun (solar wind) , in a coronal mass ejection, which take two or three days to
get here, cause the gas atoms in the sky to glow. It all depends how active the
Sun has been. Particles were usually pulled towards the North Pole but if
there were enough of them they will travel further down towards the equator .
QuadantKeele.wordpress.com – Keele University UK
As the ions approach our atmosphere at the poles it starts interacting with it.
The different colors in the aurora are produced by photons (particles of light)
that are released in the collisions between the suns wind and our
atmosphere. Photons are produced from ionized N atoms regaining an
electron, and also when O and N return to a ground (relaxed) state. O atoms
involved in collisions produce green or brown-red colors and nitrogen gives off
blue as it regains an electron or red as it returns to the ground state.
The aurora is a near daily occurrence on Earth. Because the intensity of the light in an
aurora is low, it can only be seen at night. The most active and brilliant displays
usually occur near midnight. The best time to observe the aurora is between 11 p.m.
and 2 a.m. In the northern hemisphere, the best time to view an aurora is during the
winter. At latitudes where auroras are common, it is typically light all night in the
summer—so you rarely have warm weather and a good aurora. Furthermore, in most
polar regions, the weather tends to be clear during the middle of winter—so often
the best time to see an aurora is also the coldest.
The waves radiate from the interacting charged
particles, which is why the waves are called
electromagnetic radiation.
• Electromagnetic waves consist of electric and magnetic
fields at right angles to each other and perpendicular to the
direction in which the wave is moving.
• At point A in the diagram, the field energy is at maximum
and starts to decrease, while at point B, the field is at
minimum energy and will start to increase.
• Therefore, the electromagnetic wave “leapfrogs”
through space, bouncing its energy back and forth
between electric and magnetic fields.
James Maxwell – Discovered the
existence of EM Radiation
In 1864 Maxwell, before the Royal
Society of London in 'A Dynamic
Theory of the Electro Magnetic Field',
said:
“We have strong reason to conclude
that light itself - including radiant
heat and other radiation, if any is an electromagnetic disturbance
in the form of waves propagated
through the electro-magnetic field
according to electro-magnetic laws.”
• They can travel in the
vacuum of space – no
need for a medium.
They can travel at a speed of 300,000 km/s or 186,000
miles/s. (James Maxwell wrote equations that predicted this
speed.) When EM waves travel though matter, they are still
faster than mechanical waves such as sound.
This view of the
Cartwheel galaxy was
created by combining
images captured by four
space telescopes: Galaxy
Evolution Explorer,
Hubble Space Telescope,
Spitzer Space Telescope,
and Chandra X-ray
Observatory.
Wordlesstech.com
Electromagnetic radiation may have particle
behavior as well as wavelike behavior. This is
referred to as wave-particle duality. (Tiny bundles
of light radiation are referred to as photons.)
A photon is
released as an
electron moves
back to a lower
energy level.
Electromagnetic waves are arranged by
wavelength in the electromagnetic
spectrum.
Radio waves have the longest
wavelength and the lowest frequency
on the electromagnetic spectrum.
Types of Radio Waves:
AM (amplitude modulation) – the carrier wave is
varied or modulated by changing the amplitude.
FM (frequency modulation) – the carrier wave is
modulated by altering the frequency
The radio waves of the highest frequency
and energy are called microwaves.
Microwaves in microwave ovens cook food
by causing water molecules in food to
vibrate.
Radar waves are a type of microwave energy.
Stealth technology can deflect or absorb radar waves
Stealth
ships
Infrared has a wavelength slightly longer than visible
light. Warm objects give off more infrared radiation than
cool objects which can be detected by thermal imaging.
Visible Electromagnetic Radiation - Light
Visible Light Spectrum of colors
Ionizing and nonionizing radiation
Ionizing radiation is radiation with enough energy so that
during an interaction with an atom, it can remove tightly
bound electrons from the orbit of an atom, causing the atom
to become charged or ionized. Ionizing radiation can be
hazardous to our health.
Ultraviolet Radiation - Slightly higher frequency than
visible light, it has more energetic photons.
It can stimulate skin cells to produce vitamin D, needed for
bones and teeth, but over exposure can cause skin
damage and possibly skin cancer.
X-rays – a shorter wavelength and higher frequency
than ultraviolet. It is used in medical diagnosis, as
well as airports and quality control in manufacturing.
Ways to view a galaxy
Gamma Radiation
Gamma radiation - highest frequency and most energetic
waves of the electromagnetic spectrum. They are emitted
from radioactive atomic nuclei. Concentrated gamma rays
can kill cancerous cells. It can also kill healthy cells which is
why radiation therapy can be difficult for cancer patients.