Starter: What is Light? ( you need to write an answer for this one) Goal: get some understanding of what light is and the spectrum of electromagnetic

•Starter: What is Light? ( you need to write an answer for this one)

•Goal: get some understanding of what light is and the spectrum of electromagnetic waves.

•Today we continue our discussion on Waves, simply moving into a new area of waves.

Good Morning! 04/20/23

First we need to finish the worksheet from yesterday on

Sound waves.

Link to PPT

We are going to split up and do the worksheet on the laptops

The rest will be going through a Powerpoint (.ppt) on the screens.For those going to the laptops you will be going to the usual place. Science Shares Folders Durand then open the word doc. “EMSpectrumLink”

Light is a crazy thing that we may never understand, but let me tell you what we

do know.•Light travels as a wave, a transverse, Electromagnetic Wave.•It can behave as a particle•It travels faster than anything in the universe!•It is impossible for us to travel faster than the speed of light.

The Back Story

Why does light travel so fast?

• The difference between a wave and a particle might seem obviousa wave is a disturbance that carries energy, and a particle is a piece of matter.

Waves and Particles12.112.1What are electromagnetic waves?What are electromagnetic waves?

• However, in reality the difference is not so clear.

• In 1887, Heinrich Hertz found that by shining light on a metal, electrons were ejected from the metal.


• Hertz found that whether or not electrons were ejected depended on the frequency of the light and not the amplitude.

• Because the energy carried by a wave depends on its amplitude and not its frequency, this result was mysterious.


• Years later, Albert Einstein provided an explanationelectromagnetic waves can behave as a particle, called a photon, whose energy depends on the frequency of the waves.

• Because electromagnetic waves could behave as a particle, others wondered whether matter could behave as a wave.

Particles as Waves12.112.1What are electromagnetic waves?What are electromagnetic waves?

• If a beam of electrons were sprayed at two tiny slits, you might expect that the electrons would strike only the area behind the slits, like the spray paint.

• Instead, it was found that the electrons formed an interference pattern.

Particles as Waves12.112.1What are electromagnetic waves?What are electromagnetic waves?

• This type of pattern is produced by waves when they pass through two slits and interfere with each other.

• Water waves produce an interference pattern after passing through two openings.

Particles as Waves

• It is now known that all particles, not only electrons, can behave like waves.

Electromagnetic Waves

Believe it or not, you are being “showered” all the time, not by rain but by waves.

What Is an Electromagnetic Wave?

An electromagnetic wave consists of vibrating electric and magnetic fields that move through space at the speed of light.

How do sunglasses work?

An analogy for sunglasses


Click the Video button to watch a movie about electromagnetic waves.

The Nature of Electromagnetic Waves

Electromagnetic Waves Activity

Click the Active Art button to open a browser window and access Active Art about electromagnetic waves.

Waves of the Electromagnetic Spectrum


What Is the Electromagnetic Spectrum?

The electromagnetic spectrum is the complete range of electromagnetic waves placed in order of increasing frequency.


Electromagnetic Spectrum

Click the Video button to watch a movie aboutthe electromagnetic spectrum.


Please turn in your Worksheet on Electromagnetic Spectrum

Radio and Television

In AM transmissions, the amplitude of a radio wave is changed. In FM transmissions, the frequency is changed.

Comparing Frequencies

WirelessCommunication

In the cellular phone

system, cellular phones transmit

and receive radio

waves that travel to

the nearest tower.

Documents

Starter: What is Light? ( you need to write an answer for this one) Goal: get some understanding of what light is and the spectrum of electromagnetic