Transcript Chapter 3 - The Nature of Light

Chapter 22 - The Nature
of Light
Section 1 – What Is Light?
pp. 632-635
TERMS TO LEARN
• Electromagnetic (EM) wave– a
wave that can travel through
space and matter. It consists of
changing electric and magnetic
fields.
• Radiation – the emission of
energy in the form of EM waves
LIGHT
• Light is an EM wave.
• Light can travel through space and
matter.
• A field is a region around an object
that can exert a force on another
object without actually touching it
(ex.: a magnet is surrounded by a
magnetic field that can pull a paper
clip toward it).
AN ELECTROMAGNETIC
WAVE
The Split Personality of
Light
• Scientists think that light has
the properties of both a particle
and a wave.
• This is known as the particlewave theory of light.
HOW LIGHT IS
PRODUCED
1. Electrons in an atom move around
the nucleus at different distances
depending on the amount of energy
they have. When an electron
absorbs energy, it can jump to a
new position.
2. This electron cannot stay at the
new position for very long. It then
returns to its original position,
releasing the energy it absorbed in
a tiny packet called a “photon”.
HOW LIGHT IS
PRODUCED
3. The movement of
electrons back and forth
creates a stream of
photons. This stream of
photons (the EM wave)
carries the energy released
by the electrons.
THE SPEED OF LIGHT
• In space, the speed of light is
300,000,000 m/s.
• Light travels slower in air, glass
and other types of matter.
• Light travels more than 880,000
times faster than sound!