waves: light moving waves carry energy from one place to another

WAVES: LIGHT moving

Waves carry energy from

one place to another

The NATURE of WAVES

Waves – A wave is a disturbance that transfers energy.

A medium – A substance which transmits a wave.

Speed of waves – depends on the properties of the medium.

This drawing shows

1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

This drawing shows

1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

This drawing shows

1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

This drawing shows

1. reflected energy 2. transmitted energy 3. emitted energy 4. absorbed energy

Light & the Electromagnetic Spectrum

LIGHT: What Is It?

Light Energy Atoms

As atoms absorb energy, electrons jump out to a higher energy level.

Electrons release light when falling down to the lower energy level.

Photons - bundles/packets of energy released when the electrons fall.

Light: a stream of Photons

Electromagnetic Waves

Speed in Vacuum300,000 km/sec186,000 mi/sec

Speed in Other MaterialsLight is slower in Air, Water, Glass

Transverse Waves

Energy is perpendicular to direction of motion

Moving photon creates electric & magnetic fieldLight has BOTH Electric & Magnetic

fields at right angles!

Electromagnetic Spectrum

Electromagnetic Spectrum

Radio WavesLongest wavelength & lowest frequency.

Size of a football field +Radio & T.V. broadcasting.

Electromagnetic Spectrum

Microwaves About the size of a

baseball Used in radar,

cooking, pagers, cells

Electromagnetic Spectrum

Infrared Rays Light rays with longer wavelength than red light.

Longer IR is heat Cooking, Medicine, T.V. remote controls

Which is the same thing as heat?

1. Visible light 2. Infrared light 3. Radio waves 4. Ultraviolet radiation

This drawing shows

1. convection 2. transmitted energy 3. conduction 4. absorbed energy

This drawing shows

1. convection 2. transmitted energy 3. conduction 4. absorbed energy

LandSat satellite

Electromagnetic Spectrum

Visible Spectrum – Light we can seeRoy G. Biv – Acronym for Red,

Orange, Yellow, Green, Blue, Indigo,

& Violet.Largest to Smallest Wavelength.

Electromagnetic Spectrum

Ultraviolet rays.EM waves slightly shorter than visible light

Used in food processing & hospitals to kill germs’ cells

Helps your body use vitamin D.

Electromagnetic Spectrum

X-Rays are shorter than UV rays. Medicine – Bones absorb x-rays; soft tissue does not.

Lead absorbs X-rays.

Electromagnetic Spectrum

Gamma rays Shortest wavelength EM waves. They come from outer space. Uses: cancer treatment.

The Atmosphere absorbs wavelengths

LIGHT: Particles or Waves?

Wave Model of LightExplains most properties of light

Particle Theory of LightPhotoelectric Effect – Photons of

light produce free electrons

LIGHT: Refraction of Light

Refraction – Bending of light due to a change in speed. Index of Refraction – Amount by which a

material refracts light. Prism – Glass that bends light. Different

frequencies are bent different amounts & light is broken out into different colors.

Refraction

LIGHT & Reflection

Reflection – Bouncing back of light wavesRegular reflection – mirrors smooth

surfaces scatter light very little. Images are clear & exact.

Diffuse reflection – reflected light is scattered due to an irregular surface.

Color of Light

Color of Objects White light is the presence of ALL

the colors of the visible spectrum. Black objects absorb ALL the colors

and no light is reflected back.

How You See

Retina – Lens refracts light to converge on the

retina. Nerves transmit the image Rods –

Nerve cells in the retina. Very sensitive to light & dark

Cones – Nerve cells help to see light/color

How You See

Near Sighted – Eyeball is too long and image focuses in front of the retina

Far Sighted – Eyeball is too short so image is focused behind the retina.

© 2000 Microsoft Clip Gallery

© 2000 Microsoft Clip Gallery

LIGHT & USES: LASERS

LASERSAcronym: Light Amplification by

Stimulated Emission of RadiationCoherent Light – Waves are in

phase so it is VERY powerful & VERY intense.

Summary

Waves carry energy from one place to another

The Electromagnetic Spectrum is an arrangement of 7 kinds of radiation, based on their wavelength

Each kind of radiation has different wavelengths

Each color of light has different wavelengths

Summary

Radio waves, microwaves, infrared rays, light, ultraviolet light, x-rays and gamma rays are different wavelength bands in the spectrum of electromagnetic waves

The speed of EM radiation in vacuum is approximately 186,000 miles/sec

The End…

© 2000 Microsoft Clip Gallery