Light: Electromagnetic Radiation

Important Vocabulary

Electromagnetic radiation

Photon

Radio wave

Microwave

Infrared radiation

Visible radiation

Ultraviolet radiation

X ray

Gamma ray

Fold each piece of construction paper to form a sleeve.

Insert a thermometer into each sleeve.

Place it 25 cm from a light source, record temperature

Wait 10 minutes, record temperature of each sleeve again

Color 25 cm (start) 25 cm (10 minutes after)

Color 25 cm (start)

25 cm (10 minutes after)

Black

Yellow

Orange

Blue

Electromagnetic Radiation

Transverse waves produced by electrically charged particles

They radiate from particles

The transfer of energy by electromagnetic waves is called radiation

They DO NOT need a medium to transfer energy

Travel faster than sound or water waves

Electromagnetic Radiation

Travel at the same speed in a vacuum, but frequencies and wavelengths differ

Shorter the wavelength the __________ the frequency

Radiation carries energy and momentum

Light is composed of tiny particles called photons

Photons with the highest energy correspond to light with the highest frequency

High energy photons can damage matter

Radio Waves

When you tune a radio to a station, you are adjusting to respond to radio waves of a certain frequency

Long wavelengths and low frequencies

High / Low photon energy

Used in television, cellular telephones and cordless telephones

Radio Waves

Radio waves with the highest frequency and energy are called microwaves

Used in communications and speedy cooking

Microwaves transfer energy to the water molecules that are inside food, causing them to vibrate and move faster

The result is the kinetic energy and temperature of the water molecules increase

Infrared Radiation

Infrared Radiation has a wavelength slightly longer than visible light

Think of a nice sunny day, what happens to your skin? What happens when the clouds cover the sun?

Warm objects give off more infrared radiation than cool objects

Measurements of the body’s emission of infrared radiation help doctors make medical diagnosis

Visible Radiation – light

The only part of the electromagnetic spectrum that you can see

Light can also cause chemical reactions to occur such a as:

Can stimulate decomposition reactions of materials

Ultraviolet Radiation

Why do you wear sunglasses or sunscreen in strong sunlight?

Ultraviolet radiation has a higher frequency than visible light

Photons are more energetic and have greater power than photons of visible light

Exposure to UV rays produce vitamin D, kill bacteria, and sterilize surgical instruments

Overexposure can lead to damaged skin, cancer

Ozone protects us from UV rays

Ozone

Earth’s natural filter

Blocks most of the sun’s UV rays

It is a form of oxygen where oxygen atoms cobmine to make each ozone molecule

Reduction in the ozone = an increase in UV rays

Chemicals break down ozone

X Rays

Gamma Rays

Homework p. 535 #1-3