7.6.a Students know visible light is a small band
within a very broad electromagnetic spectrum.







Wave- a disturbance that transfers energy
from place to place
Energy- the ability to do work
Disturbance is temporary- after wave is gone
medium is calm again
Most waves require a medium to travel
through
Medium- material a wave travels through
Examples of mediums: gases, liquids, solids
Waves that require a medium are mechanical
waves






A wave that doesn’t require a medium is an
electromagnetic wave (example: light)
Key concept: Mechanical waves are produced
when a source of energy causes a medium to
vibrate
Vibration- repeated back-and-forth and up-anddown motion
When a vibration goes through a medium a wave
results
Energy is needed to make a wave
When waves travel though a medium the medium
does NOT travel with the waves
Key concept: The basic
properties of all waves are
amplitude, wavelength,
frequency, and speed.

Amplitude- maximum distance that the
particles of the medium moves away from the
rest position
Crest- high point of the wave

Trough- low point of the wave

Properties of Waves
Wavelength- the distance between two
corresponding parts of the wave (example: from
crest to crest)





Frequency- number of complete waves in a
certain amount of time
Hertz-units we use when measuring
frequency
Waves travel at different speeds
Speed- far the wave travels in a given amount
of time
If the medium doesn’t change the speed
doesn’t change
What Is an Electromagnetic Wave?

Key concept: An electromagnetic wave
consists of vibrating electric and magnetic
fields that move through space at the
speed of light.




They transfer energy without a medium
Electromagnetic waves- transfers electrical
and magnetic energy
They are produced by charged particles
Every charged particle has an electric field
surrounding it




Electromagnetic radiation- energy that is
transferred through space by electromagnetic
waves
Electromagnetic waves travel at the speed of
light (about 300,000 kilometers per second)
They transfer energy through a vacuum or
empty space
When light travels through a medium it
travels slower
What Is the Electromagnetic Spectrum?

The electromagnetic spectrum is the
complete range of electromagnetic waves
placed in order of increasing frequency.
Videos:
•Exploring Light and Color: The
Electromagnetic Spectrum
•Light: The Electromagnetic
Spectrum




More frequency means more energy
Radio waves- electromagnetic waves with the
longest wavelengths and lowest frequencies
(radio and TV)
Microwaves- electromagnetic waves with the
shortest wavelengths and highest frequencies
(microwaves and cell phones)
Infrared Rays- invisible heat (heat lamps)




All electromagnetic
waves travel at the
same speed in a
vacuum but at different
wavelengths and
different frequencies
As wavelength
decreases frequencies
increases
Waves with the longest
wavelengths have the
lowest frequencies
Waves with the
shortest wavelengths
have the highest
frequencies

Key concept: The electromagnetic spectrum is made up of
radio waves, infrared rays, visible light, ultraviolet rays,
X-rays, and gamma rays.


Visible lightsmall band in the
broad
electromagnetic
wave that you can
see
Main colors of
visible light- red,
orange, yellow,
green, blue,
indigo, violet



Ultraviolet rays- wavelengths just shorter
than visible light
Ultraviolet rays carry more energy than
visible light
Exposure to small
amounts of
ultraviolet rays can
be healthy but too
much can cause
skin cancer





X-rays- wavelengths just
shorter than visible light
Has more energy than
ultraviolet rays so x-rays can
penetrate most things
Dense matter (like bone or
teeth) absorbs x-rays and
doesn't let them pass through
Gamma rays- shortest waves,
most frequency, and most
penetrating
Gamma rays are used to kill
cancer inside the body