What is light?

Does light leave the fire?

Does light from the fire reach this

couple?

Does light from the fire reach the trees in the background?

Does light from the fire reach the person who took

this picture?

Light is a form of electromagnetic radiation.

This means that light is a transfer of energy from one place to another.

Examples of Electromagnetic Radiation:

• Visible Light• Radio Waves• X Rays• All energy transport processes

How would the universe be different without electromagnetic radiation?

• A WAVE is a regular series of disturbances that moves through a material medium or through an empty space.

• An ELECTROMAGNETIC WAVE is an electric and magnetic disturbance that travels through space and transparent materials.

Are ocean “waves” really waves scientifically?

Are ocean waves electromagnetic waves?

• Electromagnetic waves move at a speed of about 3,000,000,000 meters per second, or 186,000 miles per second.

• Though they all move at the same speed, different kinds of electromagnetic waves move with different wavelengths and frequencies.

WAVELENGTH• The distance between successive crests of the wave.• Symbolized by the Greek letter lambda, λ.

FREQUENCY• The rate at which crests pass a fixed point.• Usually given in number of wavecrests per second, or Hertz (Hz).

So, WAVELENGTH is a measure of DISTANCEand FREQUENCY is a measure of TIME.

When WAVELENGTH, λ, is multiplied by FREQUENCY, f, the result is the speedof light, c.

C = λf

                                                                                                    <>

The Electromagnetic Spectrum

So a visible light wave can beMODELED as below…

But what about PHOTONS?

In the late 1700s, Isaac Newton argued that light was made up of a stream

of PARTICLES called PHOTONS

But what about PHOTONS?

But Robert Hooke and other scientists were arguing that light was made up of waves…

But what about PHOTONS?

Because of Isaac Newton’s good reputation, the

PHOTON argument was accepted for over 100

years…

Modern experiments show that light has a DUAL NATURE:• It behaves as a wave

• It behaves as a particle

Two Ways to Change the Direction of

Light:

1)REFRACT it (bend it w/ a lens!)2)REFLECT it (change it’s

direction w/ a mirror!)