Grade 8 ScienceGrade 8 Science

WAVES,LIGHT, SOUNDWAVES,LIGHT, SOUND

LIGHTLIGHT

COLOR SPECTRUMCOLOR SPECTRUM

SEEING COLORSEEING COLOR

LightLight

Light: a form of energy that can Light: a form of energy that can be detected by the human eye.be detected by the human eye.

Visible light: is a light wave that Visible light: is a light wave that you can see. It is a mixture of you can see. It is a mixture of all the colors of the rainbow.all the colors of the rainbow.

Properties of Visible Light...Properties of Visible Light...

Light travels in a straight line... Light travels in a straight line... ((rectilinear propagationrectilinear propagation))

Refraction is the bending or changing Refraction is the bending or changing direction of a wave as it passes from one direction of a wave as it passes from one material to another. material to another.

White light (sunlight) is made up of waves White light (sunlight) is made up of waves having different wavelengths and having different wavelengths and frequencies.frequencies.

•Except when white light passes through Except when white light passes through some materials. It can bend.some materials. It can bend.Light refracts (Refraction)Light refracts (Refraction)

Bent Stick

Visible Light SpectrumVisible Light SpectrumIf light waves are passed through a prism, it is refracted into a If light waves are passed through a prism, it is refracted into a rainbow of colors.rainbow of colors.Each color has a different wavelength, longer wavelengths refract Each color has a different wavelength, longer wavelengths refract less than shorter wavelengthsless than shorter wavelengths

The constituent colors of The constituent colors of white light are:white light are:

RedRedOrangeOrangeYellowYellowGreenGreenBlueBlueIndigoIndigoVioletViolet

ROY G BIV

**Red has the smallest refraction and violet has the greatest.

Light and The Light and The Electromagnetic SpectrumElectromagnetic Spectrum

Visible light (the light we see) is Visible light (the light we see) is only a small portion of the waves only a small portion of the waves around us.around us. There are invisible waves There are invisible waves around us, some are travelling around us, some are travelling right through us. right through us.

Frequency, Wavelength and Frequency, Wavelength and EnergyEnergy

The longer the wavelength, the lower the The longer the wavelength, the lower the frequencyfrequencyA. Wave passes through an area once in a A. Wave passes through an area once in a

second. Frequency = 1 Hertzsecond. Frequency = 1 Hertz

B. 4 waves pass through the same area in a B. 4 waves pass through the same area in a second. Frequency = 4 Hertzsecond. Frequency = 4 Hertz

What wave has the highest frequency?What wave has the highest frequency?

““B” has the highest frequency B” has the highest frequency

““B” has the shortest wavelengthB” has the shortest wavelength

What wave has the most energy?What wave has the most energy?

• “ “B” has the most energy because it has B” has the most energy because it has the highest frequency and it has the the highest frequency and it has the shortest wavelengthshortest wavelength

High frequency waves High frequency waves have shorter wavelengths have shorter wavelengths and produce more energy and produce more energy

Electromagnetic RadiationElectromagnetic Radiation

The transmission of energy in The transmission of energy in the form of waves that the form of waves that extend from the longest extend from the longest radio waves to the shortest radio waves to the shortest gamma rays.gamma rays.

Types of Electromagnetic Types of Electromagnetic RadiationRadiation

1.1. Radio wavesRadio waves2.2. MicrowavesMicrowaves3.3. Infrared WavesInfrared Waves4.4. Visible Light SpectrumVisible Light Spectrum5.5. Ultraviolet WavesUltraviolet Waves6.6. X-RaysX-Rays7.7. Gamma Rays Gamma Rays Electromagnetic Spectrum Song

Electromagnetic SpectrumElectromagnetic Spectrum

Light and the Electromagnetic SpectrumLight and the Electromagnetic Spectrum

The visible spectrum is a tiny portion of a much larger The visible spectrum is a tiny portion of a much larger spectrum of radiation called the electromagnetic spectrum of radiation called the electromagnetic spectrum.spectrum.

Electromagnetic radiation is transmission of energy from Electromagnetic radiation is transmission of energy from the longest radio waves to the shortest gamma waves.the longest radio waves to the shortest gamma waves.

See pages 152 - 154

Types of Electromagnetic RadiationTypes of Electromagnetic Radiation1.1. Radio wavesRadio waves: :

the longest wavelength and lowest energy and the longest wavelength and lowest energy and frequency.frequency.Can be used to help us see the inside of our Can be used to help us see the inside of our bodies to diagnose illness. Ex.bodies to diagnose illness. Ex. MRI MRI

Magnetic Resonance Imaging

2. 2. MicrowavesMicrowaves::have the shortest wavelength and the highest have the shortest wavelength and the highest frequency of all radio waves.frequency of all radio waves.Ex. Microwave ovens, telecommunication Ex. Microwave ovens, telecommunication satellites, radio telescopes, radar (remote sensing)satellites, radio telescopes, radar (remote sensing)

Microwave ovens use a specific frequency that is strongly absorbed by water molecules in food.

3. 3. Infrared WavesInfrared Waves::

longer wavelength = lower energy and longer wavelength = lower energy and frequency.frequency.Infrared means below redInfrared means below redAlso called heat radiationAlso called heat radiationEx. Remote controls, computer, heat Ex. Remote controls, computer, heat lamps, motion sensorslamps, motion sensors

Infr

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LANDSAT Image of

Fire

4. 4. Visible Light SpectrumVisible Light Spectrum

Can be continually detected by our eyes.Can be continually detected by our eyes.(look back at slide 12)(look back at slide 12)

5. 5. Ultraviolet Waves (UV)Ultraviolet Waves (UV)::shorter wavelength =higher energy and shorter wavelength =higher energy and frequency. (frequency. (Just beyond the visible region of the spectrum.)Just beyond the visible region of the spectrum.)

Very energeticVery energeticHave the ability to kill bacteria in food and water Have the ability to kill bacteria in food and water and medical supplies.and medical supplies.Ex. Sun, Ex. Sun,

Wearing sunglasses and sunscreen help protect you against harmful UV radiation.

Wavelengths shorter than Visible LightWavelengths shorter than Visible Light

6. 6. X-RaysX-Rays::have a shorter wavelength = higher energy and have a shorter wavelength = higher energy and frequency than UV.frequency than UV.

Used to photograph teeth, bones and the inside of Used to photograph teeth, bones and the inside of machines, security screeningmachines, security screening

X-Ray Imaging

7. 7. Gamma RaysGamma Rays::have the shortest have the shortest

wavelength = the highest wavelength = the highest energy and frequency in the energy and frequency in the electromagnetic spectrum.electromagnetic spectrum.

Result from nuclear reactions.Result from nuclear reactions.

Produced by the hottest Produced by the hottest regions of the universe.regions of the universe.

Gamma rays can be used to kill cancer cells.