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Waves, EM spectrum Mr. Sroka science
What is a wave?
A wave can be
described as an energy
disturbance that travels
through a medium from
one location to another.
Waves, simply put, are
energy moving from
one place to another.
How do they move?
As the wave moves through the medium (water, slinky, air), energy is being passed from one particle to the next. Waves occur around us every day. Some common places we experience waves are in sound, light, water, and earthquakes.
Two basic types of waves!
In a longitudinal wave
the particles move
parallel to the direction
the wave is moving.
In a transverse wave
the particles move at
right angles to the
direction of wave travel.
Wave characteristics!
Wavelength
Wavelength – The
length of a wave. This
can be measured easily
from crest to crest or
from trough to trough.
Frequency
Frequency – The
number of waves
produced in a given time
period. This is usually
measured in waves per
second called Hertz
(Hz).
Wave Speed v = c x f
Velocity = wavelength x frequency
This is the same formula we use for the speed of light
however the V gets changed to a lower case c.
Practice problems on the board!!!
Mechanical wave
Sound is a mechanical
wave that results from
the back and forth
vibration of the particles
of the medium through
which the sound wave is
moving.
Video
Electromagnetic Waves
EM waves for short
Electromagnetic waves are
waves which can travel
through the vacuum of outer
space.
Mechanical waves, unlike
electromagnetic waves,
require the presence of a
material medium in order to
transport their energy from
one location to another
Types of EM waves
Radio waves
Mircowave
Infrared waves
Visible light
Ultraviolet
X-rays
Gamma rays
What can we see???
LET THERE BE LIGHT!!!
Understanding the EM
spectrum allows
astronomers to study
the universe.
Think about it
Andromeda Galaxy is
roughly 2.5 million LYA.
For example The Sun The Sun emits lights in all
wavelengths – our eyes can only
see one small range of
wavelengths (i.e. visible light).
All the action takes place at the
wavelengths our eyes cannot
see. If you place different filters
over the cameras, you can
capture only the light that can get
through that filter.
We determine temperature of
distance objects this way
What else can we do?
Formation of a
Spectrum!
A spectrum splits light
into its wavelengths.
This is done by the use
of a spectroscope
Astronomers can use the spectral lines to
determine what stars and
galaxies are made of!
The Doppler Effect
The Doppler effect is
the change in frequency
of a wave for an
observer moving relative
to its source.
HUH??? It’s the change
in pitch you hear as an
ambulance passes.
Connection to Outer Space We can use the Doppler
effect to determine if things
are moving towards or away
from earth!
redshift/blueshift happens
when light or other
electromagnetic radiation
shifted to one end of the
spectrum.
Red longer away
Blue shorter towards
Summary - what can we
use star light for???
Temperature - Wein’s
law
Composition - spectral
lines
Direction and speed -
red/blue shift