Electromagnetic Waves
are made by vibrating electrical forces that travel
through space – but do NOT require matter to travel
Electromagnetic Waves have a wavelength and a frequency:
Wavelength = the distance between the crest of two waves
Frequency = the number of waves that pass a point in 1 second
The energy of a wave is related to wavelength and frequency – how?
The Electromagnetic Spectrum
Is composed of energy having different
wavelengths and frequencies
Higher frequency
waves = more energy.
The energy we detect
with our eyes is
VISIBLE LIGHT
The speed of energy waves in space is referred to as
"speed of light"
This is nature's speed limit – we know of nothing that travels faster!
If travel is to occur to
distant planets and
galaxies, we need to
find a way to exceed
the speed of light!
Radio Waves
We are surrounded by radio waves that
we cannot see.
(Where are they on the electromagnetic
spectrum?)
The radio or TV antenna receives the
radio waves and converts them to
different forms of energy - sound waves
or light waves that you can hear or see.
Radio waves have different frequencies for each station/supplier.
You tune your radio or TV receivers by choosing a frequency.
Radar - uses radio waves to find the
position and movement of objects
stands for RAdio Detecting And Ranging
Radar devices
measure the time
required for radio
waves to bounce off
an object, like a car.
The measured time
is converted into the
object’s positions
(and thus, speed).
Microwaves
Microwave ovens turn electricity into
microwaves. that causes water
molecules to move back and forth,
which in turn causes HEAT.
Intense microwaves can damage living cells and tissue – hence,
they are enclosed by strong metal boxes that do not allow
the waves to escape.
Weak microwaves can carry information
– such as those used by cellphones.
Infrared Waves – transmit heat, and are used to
detect living creatures in the absence of visible light.
Objects that are living (use energy or that metabolize
food) can be distinguished from the environment by
infrared waves.
Ultraviolet (UV) Waves have shorter
wavelengths and more energy than visible light,
and can enter cells. A small amount may be
good, but too much can cause sunburn and
cause blisters and damage your DNA
X Rays and Gamma Rays
Both are high energy waves and
are damaging if you are exposed
to them without protection
X Rays can be used to
form images of bone and
teeth (how do these
Work for Superman?)
Gamma Rays - can be
used to target and kill
cancer cells (radiation therapy)
Visible Light
Violet = shortest wavelength seen
Red = longest wavelength seen
Transparent materials
(glass, water, plastic)
pass visible light, but
may block UV and
infrared waves.
Glass is not transparent
to most UV, this is why
you cannot get a sunburn
through a window.
Opaque - materials that are not transparent
Tights are labeled as either sheer
(transparent) or opaque; which
ones are pictured here ?
Why is wet sand darker than dry sand?
Light reflecting from a dry surface goes directly to your
eyes. However, as light is reflected from wet surface, some of
it is scattered and absorbed - making it appear darker.
The ocean and sky
are blue because
water and air absorb
red light and scatter
blue light that we see.
At sunset and sunrise,
we can see sunlight
that is not reflected,
but do not look very
long – as it may
damage your eyes!
Color is determined by the receiver – which
perceives the wavelength of light that reflects from or
is emitted by an object.
What color is.....
The sky? ______________________
An apple? ______________________
The grass ? ______________________
Can you explain why?
If you are colorblind, you cannot perceive which colors?
Can you explain why?
How we see colors depends on whether the
object absorbs or reflects particular wavelengths.
White objects reflect all visible light
Black objects absorb all visible light
White light passed through a prism causes the different energy
wavelengths to separate, which are perceived as individual colors.
Primary Colors
Red, Green & Blue are the primary colors. These colors
combine to create any other color in the visible
spectrum. All three combined will create white light.
Red + Blue = magenta (purple)
Blue + Yellow = green
Red + Yellow = orange
Opposites on this color
wheel contain all three
primary colors and form
white light.