1. Chapter 22 The Nature of Light
Section 1 What is light?

2. Terms to Learn
Electromagnetic (EM) waves are transverse waves consisting of changing electric fields and magnetic fields.
Light is an EM wave.
EM waves are transverse waves.

3. How are they produced? Electric Field
– Exerts electric force on charged particles. Can be
produced by changing magnetic fields
Magnetic Field
– Exerts magnetic forces and can be produced by
changing electric fields.
Electromagnetic waves are produced when an
electric charge vibrates or accelerates. In other
words it is produced in constantly changing
fields.

4. Terms to Learn
Radiation: is the emission of energy in the form of EM waves.
An EM wave is produced by the vibration of an electrically charged particle.
Photons: a tiny “packet” of energy that is released by an electron that moves to a lower energy level in an atom.

5. The Split Personality of Light
Scientists think that light has the properties of both a particle and a wave.
This is known as the particle-wave theory of light.

6. The Production of Light
Electrons move about the nucleus at different distances depending on the amount of energy they have. When it absorbs energy it can jump to a new position.
This new position is usually unstable, the electron will not stay there long and will return to its original position releasing the energy it absorbed in a tiny packet called a photon.
The movement of electrons back and forth creates a stream of photons. This can be thought of as a waves of vibrating electric and magnetic fields. These photons (EM waves) carry the energy released by the electrons.

7. The Speed of Light
Scientist have yet to discover anything in the universe faster than light.
In space light travels about 300,000,000m/s
It travels slower in air, glass and other types of material.
Although it does not require a medium it can travel through many substances.