WAVES: SOUND & LIGHT Waves carry energy from one place to another © 2000 Microsoft Clip Gallery

NATURE OF WAVES Waves (Def.) – A wave is a disturbance that transfers energy. Medium – Substance or matter (molecules) through which a wave is transmitted. Speed of Waves – Depends on the properties of the medium.

Wavelength Def: Distance from the peak of one wave to the peak on the next wave Can be measured in: kilometerskm1,000 metres metersmAwww, come on, you know how big a meter is! centimeterscmA hundredth of a meter. But you know this already. millimetersmm1/1000th of a meter. Those tiny lines on your ruler! nanometersnm 1/1000,000,000th of a meter. Or, if you prefer, a millionth of a millimeter. Small!

Frequency Def: How many waves per second Can it be measured in: HertzHz1 Hz means 1 wave per second kilohertzkHz1 kHz is 1,000 waves per second Megahertz MHz 1 MHz is 1 million waves per second. Your favorite FM radio station probably broadcasts around 100 MHz Gigahertz GHz 1 GHz is 1,000 million waves per second. Microwaves are around a few GHz.

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: Stream of Photons © 2000 Microsoft Clip Gallery

Electromagnetic Waves Speed in Vacuum/Empty Space (No molecules) 300,000 km/sec 186,000 mi/sec Speed in Other Materials Slower in Air, Water, Glass EM Waves travel best in empty space!

Transverse Waves Energy is perpendicular to direction of motion Moving photon creates electric & magnetic field Light has BOTH Electric & Magnetic fields at right angles! © 2000 Microsoft Clip Gallery

Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency

Electromagnetic Spectrum Visible Spectrum – Light we can see Roy G. Biv – Acronym for Red, Orange, Yellow, Green, Blue, Indigo, & Violet. Largest to Smallest Wavelength.

Electromagnetic Spectrum Invisible Spectrum Radio Waves Def. – Longest wavelength & lowest frequency. Uses – Communication, Radio & T.V. broadcasting. © 2000 Microsoft Clip Gallery

Radio Waves Continue Modulation - variation of amplitude or frequency when waves are broadcast AM – amplitude modulation Carries audio for T.V. Broadcasts Longer wavelength so can bend around hills FM – frequency modulation Carries video for T.V. Broadcasts © 2000 Microsoft Clip Gallery

Electromagnetic Spectrum Invisible Spectrum (Cont.) Microwaves Rays Def – Shorter wave length then radio. Uses: Cooking, cell phones, and radar

Short Wavelength Microwave Invisible Spectrum (Cont.) Infrared Rays Def – Light rays with longer wavelength than red light. Given off by hot objects Uses: Cooking, Medicine, T.V. remote controls

Electromagnetic Spectrum Invisible spectrum (cont.). Ultraviolet rays. Def. –frequency slightly higher than visible light Uses: food processing, hospitals to kill cells, tanning beds, security Skin absorbs its - helps your body use vitamin D.

Electromagnetic Spectrum Invisible Spectrum (Cont.) X-Rays Def. – waves shorter than UV rays. Uses: medical imaging – Bones absorb x-rays; soft tissue does not, security screening Passes thru most material - Lead absorbs X-rays.

Electromagnetic Spectrum Invisible spectrum (cont.) Gamma rays Def. Highest frequency; Shortest wavelength. They come from outer space/stars. Uses: sterilizes medical equipment, cancer treatment.

EM Spectrum in Astronomy If we could only observe in visible light, our knowledge of the universe would be greatly limited By looking at objects at different wavelengths, we get a different view and lots more information Some objects are only visible at certain wavelengths

The Sun at Different Wavelengths VisibleUltraviolet X-ray

The Behavior of Waves What is reflection? When a wave bounces off an object and changes direction – this is reflection.

What is refraction? Refraction is the bending of a wave as it passes from one medium to another. A wave travels at different speeds in different things. When a wave traveling a certain speed moves into another medium, it will either increase in speed or decrease in speed, resulting in a change in direction.

Refraction (Cont.)

What is diffraction? Diffraction occurs when an object causes a wave to change direction and bend around it.

What is diffraction? Diffraction occurs when an object causes a wave to change direction and bend around it.

The End… © 2000 Microsoft Clip Gallery