Table of Contents

9.1

Waves of the Electromagnetic Spectrum

Ms. De Los Rios

7th

Waves and Light

Vocabulary 9.1Electromagnetic Wave- A wave made up of a combination of changing electric field and a changing field. A wave that can transfer electric and magnetic energy through the vacuum of space.

Electromagnetic Radiation- The energy transferred through space by electromagnetic waves.

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

radio waves- Electromagnetic waves with the longest wavelength and lowest frequencies.

Microwaves- Electromagnetic waves that have a shorter wavelength and higher frequencies that radio waves.

Radar- A system that uses reflected radio waves to detect objects and measure their distance and speed.

Infrared Rays- Electromagnetic waves with shorter wavelength and higher frequencies than microwaves.

Vocabulary 9.1

Thermogram- An image that shows regions of different temperatures in different colors.

Visible light- Electromagnetic radiation that can be seen with the unaided eye.

Ultraviolet Rays- Electromagnetic waves with wavelength shorter than visible light but longer than X-rays.

X-rays- Electromagnetic waves with wavelengths shorter than ultraviolet rays but longer than gamma rays.

Gamma rays- Electromagnetic waves with the shortest wavelengths and highest frequencies.

Prefix thermo= Greek word thermos means “warm or hot”

Characteristics of Electromagnetic Waves pg. 315

The sun’s energy reaches Earth in the form of electromagnetic waves (E.W.)

•An electromagnetic wave is made up of vibrating electric and magnetic fields that move through space or some medium at the speed of light.

•The energy transferred by electromagnetic waves through space or matter is called electromagnetic radiation.•E. W. do NOT require a medium such as air, they travel through empty

space.

Electromagnetic WaveAn electromagnetic wave travels through space at the speed of light—about 300,000 kilometers per second.

Waves of the Electromagnetic Spectrum pg. 315

How Do Electromagnetic Waves Compare? pg. 316

2. Frequency- Is the number of waves that pass a given point in a certain amount of time.

The frequency of a wave determines how much energy the wave has.

E.W. have different:

1.Wavelengths- Is the distance between the crest of one wave and the crest of the next wave.

How Do Electromagnetic Waves Compare? pg. 316

A vacuum is a space that contains no air or gas.

All electromagnetic waves travel at the same speed in a vacuum.

All electromagnetic waves have

different wavelengths different frequencies.

• For waves in any medium, as the wavelength decreases, the frequency increases.

•The higher the frequency of a wave, the higher its energy.

Important Information pg.316

•Each E.W. has properties that make it useful for some purposes than others.

•Visible light is the only range of wavelength that your eyes can see.

•E. W. do NOT require a medium such as air, they travel through empty space.

•Long wavelength= Low frequency= Low energy (L, L,L)

•Short wavelength=High frequency= High energy (S,H,H)

Example: Ocean waves

Important Information pg.316

• We know about these waves from the sun through observation-NOT experiment.

•A spectrograph can be used to show the sun’s radiation include all these different types of waves.

Comparing Electromagnetic WavesDifferent types of electromagnetic waves have different

wavelengths. Which are the visible light, radio waves, and X-rays?

Waves of the Electromagnetic Spectrum pg. 316

What Makes up the Electromagnetic Spectrum? pg. 317

There are many different types of electromagnetic waves.

The electromagnetic spectrum is made up of:

Mnemonic Device to Memorize the Electromagnetic Spectrum

Geniuses eXpect Ultraviolet Light In My Rainbow

Gamma radiationX-ray radiation

Ultraviolet radiationvisible radiation (Light)

Infra-red radiationMicrowave radiation

Radio waves

How Do Electromagnetic Waves Compare? pg. 317

Radio Waves (L,L,L) E.W. with the longest wavelengths(distance crest to crest) and the lowest

frequencies (# of waves that pass at a certain point in a given time)

•They are used in broadcasting to carry signals for radio programs.

Broadcasting stations sends out certain frequencies radio picks up waves, converts them into electrical signal converted into sound.

Waves of the Electromagnetic Spectrum pg. 317The Electromagnetic Spectrum

The electromagnetic spectrum can be broken up into different categories. Use the word bank to complete the boxes in the

diagram.

How Do Electromagnetic Waves Compare? pg. 318

Microwaves (S,H,H)

have shorter wavelengths(crest) and higher frequencies(#) than radio waves.

•Microwaves have many uses, including cellular phone and radar, a system that uses reflected microwaves to detect objects and measure their distance and speed.

What Makes Up the Electromagnetic Spectrum?pg. 318

Infrared rays (S,H,H)

They have wavelengths shorter than those of microwaves.

•The invisible heat you feel from stove is infrared

radiation.

• Because you feel the energy of infrared rays as

heat is called heat rays.

•Warmer objects give off infrared rays with more

Energy and higher frequencies than cooler objects.

•An infrared camera uses infrared rays instead of light to take a picture called a thermogram that shows regions of different temperatures in different colors.

Thermogram

What Makes Up the Electromagnetic Spectrum? pg. 318

Visible Light (S,H,H)These electromagnetic waves you can see.

•Visible light waves have shorter wavelengths and higher frequencies than infrared rays.•Visible light appears white, but is a mixture of many colors.•Light waves bend or refract when they enter a new medium.

•When light passes through rain= RAINBOW

How does a prism separate colors?

Mnemonic Device to Memorize the Visible Light Spectrum

ROY G BIVR: red

O: orange Y: yellow G: green

B: blue I: indigo V: violet

What Makes Up the Electromagnetic Spectrum?

Ultraviolet rays (S, H, H)

•Electromagnetic waves with wavelengths just shorter than those of visible light are called UV.

• Too much exposure to U.V. can damage or kill living cells.

•Its found naturally in sunlight. We cannot see it but we can feel it, our body responds to it by turning darker.

•Small doses of UV rays are useful, for example, cause skin cells to produce vitamin D (Bones & teeth)

•UV radiation is used in sun beds & fluorescents light

What Makes Up the Electromagnetic Spectrum?

X-rays (S, H, H)

•Electromagnetic waves with wavelengths just shorter than those of ultraviolet rays are called X-rays.

• Because of their high frequencies, X-rays carry enough energy to penetrate most matter.

•X-rays pass through soft skin and tissue but not

Dense matter, such as bone or metal.

• Bones absorbs X-rays so they do not pass through.

•Therefore, X-rays are used to make images of bones and teeth.

•Too much exposure to x-rays can cause cancer.

•X-rays can be used for in industry and engineering—x-ray structures to find cracks or damage.

What Makes Up the Electromagnetic Spectrum?

Gamma rays (S,H,H)•Electromagnetic waves with the shortest wavelengths and highest frequencies are called G.R.

•Since they have the greatest amount of energy, G.R. are the most penetrating of electromagnetic waves.

•G.R. pass through soft skin and tissue, some of it is absorbed by cells.

•They are used to examine the body’s internal structures, sterilize surgical instruments, and to kill harmful bacteria in food.

•G.R. can also be used to target and kill cancer cells.

•Exposure to G.R. is dangerous, as it can make cells cancerous.

What Makes Up the Electromagnetic Spectrum?

The Environmental Protection Agency of the United States tracks ultraviolet light levels in Texas and throughout the country. The agency’s UV index rates ultraviolet exposure on a scale of 1 to 11+. High ratings result in UV exposure warnings. These warnings let people know how long they can be out in the sun safely without sunblock.

Example of Electromagnetic Waves

Types of WavesThe electromagnetic spectrum includes many kinds

of waves. Identify each kind of wave on the electromagnetic spectrum. What is the name of the highest energy waves?

Waves of the Electromagnetic Spectrum

Online resources

http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/radiation/anintroductiontowavesact.shtml

BBC Waves Activity

The electromagnetic spectrum activity

Electromagnetic Spectrum NASA

Examine the sun at different wavelengths

Frequency & Wavelength Activity

Brainpop Waves 

Brainpop Electromagnetic Waves

Brainpop Color

Brainpop Rainbow

Brainpop Light

http://sammyholmes.wikispaces.com/Wave+Interactions

http://app.discoveryeducation.com/player/?assetGuid=0bbc28bf-4861-4601-8a36-b3576ecee9ab&fromMyDe=0&isPrinterFriendly=0&provider=&isLessonFromHealth=0&productcode=DSC&isAssigned=false&includeHeader=YES&homeworkGuid=