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 DISTANCE and FREQUENCY is a measure of TIME. When WAVELENGTH, λ, is multiplied by FREQUENCY, f, the result is the speed of light, c. C = λf

<> The Electromagnetic Spectrum

So a visible light wave can be MODELED 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!)