2-1: Waves and the Electromagnetic
Spectrum
What causes waves?
What are the basic properties of waves?
What does an electromagnetic wave consist of?
What are the waves of the electromagnetic
spectrum?
What is a wave?
• A wave is a disturbance that transfers energy
from place to place
• Energy = the ability to do work
Properties of Waves
• Waves can be very different, but all waves
share 4 basic properties:
1) amplitude
2) wavelength
3) frequency
4) speed
Wavelength = distance
between to corresponding
parts of a wave.
Amplitude = Wave height,
or how far a wave moves
from its rest position.
Crest = Highest point of
wave.
Trough = Lowest point of
wave.
• Frequency = number of
complete waves that
pass a given point in a
certain amount of time
• Speed = how far a wave
travels in a certain
amount of time
Mechanical Waves:
• Transfer energy but require
a medium to travel through
• Example: Ropes, waves in
water
Electromagnetic
Waves:
• Transfer energy but do not
require a medium
• Has vibrating electric and
magnetic fields that move
through space at the speed
of light
• Example: light, x-rays
Electromagnetic Waves
• Believe it or not, you are being “showered” all
the time, not by rain but by waves.
What Is the Electromagnetic
Spectrum?
• The electromagnetic spectrum is the complete
range of electromagnetic waves placed in
order of increasing frequency.
Visible light
• Electromagnetic waves you can see are called
visible light
• Only a small band on the broad
electromagnetic spectrum
• In order from largest to shortest wavelength:
ROY G BIV (What does that stand for?)
RED, ORANGE, YELLOW, GREEN,
BLUE, INDIGO, VIOLET
2-2: Visible Light
and Color
How does visible light interact with
an object?
What determines the color of an
opaque object?
When Light Strikes an
Object
• When light strikes an
object, the light can be
reflected, transmitted, or
absorbed.
• Most materials can be
classified as transparent,
translucent, or opaque
based on what happens
to light that strikes it.
Transparent Materials
•
•
•
•
See-through
Example: clear glass
Transmits most of the light that strikes it
Particles of the material absorb the light, then
send it back out
Translucent Materials:
•
•
•
•
Can see through it , but blurry
Example: wax paper, frosted glass
Transmits some of the light
Scatters light as it passes through material
Opaque Materials:
•
•
•
•
Not see-through
Example: construction paper, wood
Reflects or absorbs all of the light that strikes it
Can’t see through material, because light cannot
pass through it
• The color of an opaque object is the color of the
light it reflects
• Example: a lemon absorbs all colors of light, but
reflects yellow light