EM spectrum and wave.pptx

Learning Competencies/Objectives:
A.Describe how electromagnetic (EM) Wave is
produced and propagated.
B.Compare the relative wavelengths, frequencies
and energies of the different regions of he
electromagnetic spectrum.
C.Cite examples of practical applications of the
different regions of EM waves.

What is Electromagnetic Spectrum?
Electromagnetic Wave?

Can light travel
through a Vacuum
(i.e., empty space)?
Can sound travel to a vacuum?

Electromagnetic waves are created
by the vibration of an electric charge.
This vibration creates a wave which
has both an electric and a magnetic
component.

•An electromagnetic wave
is a type of wave that can
travel through empty
space example light...

Unlike sound waves, which
need "something" to travel
through (for example, water or
air), electromagnetic waves are
able to travel through
"emptiness" or a vacuum.

An electromagnetic wave transports its energy
through a vacuum at a speed of 3.00 x 108 m/s (a
speed value commonly represented by the
symbol c). The propagation of an electromagnetic
wave through a material medium occurs at a net
speed which is less than 3.00 x 108 m/s.

Hans Christian Oersted
1777-1851
OMG! The compass
needle move near the
current-carrying wire.
This shows electric
current creates magnetic
field.
Activity 1: How it came about…
http://www.rare-earth-magnets.com/hans-christian-
oersted/
http://en.wikipedia.org/wiki/Heinrich_Hertz
http://simple.wikipedia.org/wiki/Michael_Faraday
http://soulconnection.net/glossary_in_depth/maxwell.html
Image credit:

Hey Hans, the opposite
could be true! A changing
magnetic field produces an
electric field.
http://www.rare-earth-magnets.com/hans-christian-oersted/
Michael Faraday
1791-1867
Image credit:

Heinrich Hertz
1857-1894
You got it right
Maxwell. I proved
the existence of EM
waves!
Image credit:

James Clerk Maxwell
1831-1879
You both got it right! An
electromagnetic wave exists
when the changing magnetic
field causes a changing
electric field, which then
causes another changing
magnetic field, and so on.
Image credit:

EM spectrum is a
continuum of EM waves
arranged according to
frequency and
wavelength.

It shows a gradual progression
from the waves of lowest
frequency to the waves of highest
frequency or vice versa.
The different EM waves do not
have exact dividing region.

Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/e
mspectrum1.html
Newton set up a prism near his window, and
projected a beautiful spectrum 22 feet onto
the far wall. Further, to prove that the prism
was not coloring the light, he refracted the
light back together.
Image credit:
http://www.webexhibits.org/colorart/bh.html
The modern
understanding of
light and color
begins with Isaac
Newton.

Image Credit:
http://imagine.gsfc.nasa.gov/science/toolbox/emspe
ctrum1.html
Image credit:
http://coolcosmos.ipac.caltech.ed
u/cosmic_classroom/ir_tutorial/di
scovery.html
Frederick William
Herschel
(1738 - 1822)
In 1800 he performed a famous experiment where
he tried to measure the temperature of different
colours of the spectrum by placing a thermometer
on each colour. He found to his amazement that the
hottest part of the spectrum was in a place where
there was no colour at all. It was a spot beyond the
red end of the spectrum. For the first time it was
possible to talk about invisible light. This hot light
became known as Infra Red (below the red) because
it was shown to have longer wavelength than visible
light. [http://www.krysstal.com/spectrum.html]

Image Credit:
ctrum1.html
Johann Wilhelm Ritter
(1776 - 1810)
Image credit:
http://coolcosmos.ipac.caltech.edu/cosmic
_classroom/classroom_activities/ritter_bio.
html
In chemistry at that time there was a rumour that blue light
was more efficient at initiating chemical change than red
light. Ritter tried to measure the speed at which silver
chloride broke down with different colours. He proved that
blue light was indeed more efficient that red light. He was
amazed, however, that the most vigorous reactions took
place in the region beyond the violet where nothing could
be seen.
This new radiation was originally called Chemical Rays but is
now called Ultra Violet (beyond the violet). Ultra Violet
differs from visible light only in its wavelength which is
shorter. [http://www.krysstal.com/spectrum.html]

Image Credit:
ctrum1.html
Heinrich Rudolf Hertz
(1857 - 1894)
Image credit:
http://en.wikipedia.org/wiki/Heinr
ich_Hertz
He set up electric circuits that produced
oscillations and managed to produce
electromagnetic radiation with a wavelength
of 66cm (over a million times longer than
light). This radiation could be picked up by
other circuits set up quite a distance away. The
new radiation was first called Hertzian Waves;
this became Radiotelegraphic Waves after
Marconi. We now call them Radio Waves.
[http://www.krysstal.com/spectrum.html]

Image Credit:
ctrum1.html
Perry Spencer (1894 - 1970) invented the
microwave oven
In 1945, Percy Spencer was experimenting with a new
vacuum tube called a magnetron while doing research for
the Raytheon Corporation. He was intrigued when the candy
bar in his pocket began to melt, so he tried another
experiment with popcorn. When it began to pop, Spencer
immediately saw the potential in this revolutionary process.
In 1947, Raytheon built the first microwave oven, the
Radarange.
[http://science.howstuffworks.com/innovation/scientific-experiments/9-things-
invented-or-discovered-by-accident2.htm]
The scientists discovered the cosmic
microwave background radiation. This
radiation, which fills the entire Universe, is
believed to be a clue to it's beginning,
something known as the Big Bang.
Arno Penzias and Robert Wilson

Image Credit:
ctrum1.html
Wilhelm Conrad Roentgen
(1845 - 1923)
On the night of 5 November 1895, he noticed a glow coming
from a chemical called barium platinocyanide. This chemical
glowed whenever the tube was on, even if he put cardboard
between it and the tube.
Roentgen went on to show that the glow was caused by a
highly penetrating but invisible radiation given off by the
tube. It passed through paper, thin sheets of metal, flesh. It
could ionise gases and had wave properties like light but
only much shorter wavelengths.
The new radiation was called X-Rays because of their
mysterious properties. Roentgen refused to patent the
discovery or make any financial gain out of it but he was
awarded the first ever Nobel Prize for Physics.
[http://www.krysstal.com/spectrum.html]
Image credit:
http://www.two-views.com/article_Rontgen.html

Image Credit:
ctrum1.html
Villard discovered gamma radiation in 1900, while studying
radiation emitted from radium. Villard knew that his
described radiation was more powerful than previously
described types of rays from radium, which included beta
rays, first noted as "radioactivity" by Henri Becquerel in
1896, and alpha rays, discovered as a less penetrating form
of radiation by Rutherford, in 1899. However, Villard did not
consider naming them as a different fundamental type.
Villard's radiation was recognized as being of a type
fundamentally different from previously named rays, by
Ernest Rutherford, who in 1903 named Villard's rays
"gamma rays" by analogy with the beta and alpha rays that
Rutherford had differentiated in 1899.
[http://en.wikipedia.org/wiki/Gamma_ray]
Paul Ulrich Villard
(1860 - 1934)
Image credit:
http://en.wikipedia.org/wiki/Paul_Ulrich_Villard

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