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Waves, Sound, and Light MENU Mechanical Waves Wave Properties Electromagnetic Waves Sound Speed of Sound Light Transparent, Translucent, Opaque Color Click above to be taken to that section of the Power Point

Waves 2 types of waves Mechanical Use matter to transfer energy through a medium Electromagnetic Do not need matter to transfer energy

Mechanical Waves Waves that REQUIRE a medium for the energy to travel Examples: water waves, sound waves, energy moving through a slinky. What else?

Mechanical Waves Use matter (Medium) to transfer energy. The energy is transferred from particle to particle. SOUND IS A MECHANICLE WAVE

There Are Two Basic Types of Mechanical Waves. Transverse Waves The energy traveling through the wave causes the particles to move at a right angle to the direction of the energy. This is what we usually draw when representing waves. Ripples on a pond are an example of these.

The Second type of Mechanical Wave Compressional Waves In this type the particles move in the same direction as the energy. Sound is a Compressional Wave

Wave Properties Amplitude Wavelength Frequency Human perception of amplitude – loudness Human perception of frequency – pitch

Transverse Waves Crest – very top of wave Trough – very bottom of wave Amplitude – Distance between resting position and crest/trough Wavelength – Distance from the top of one crest to the next crest Frequency – Number of wavelengths to pass by a given point in 1 second 2.5 in picture at right

Transverse Waves (cont.) Frequency and Pitch As frequency increases pitch gets higher As frequency decreases pitch gets lower

Transverse Waves (cont.) Frequency and Wavelength As frequency increases wavelength decreases As frequency decreases wavelength increases

Compressional Waves Medium travels slightly back and forth in the same direction as the energy is moving

Electromagnetic Waves Waves that DO NOT require a medium for the energy to travel Examples: Light, radio waves, x-rays, gamma rays, etc. All waves on the electromagnetic spectrum

Electromagnetic Waves These waves do not need matter to travel Difference between the different waves is wavelength EM spectrum illustrates the differences

Electromagnetic Waves (cont.) Radio – listen to your favorite station Microwaves – call your friends Infrared – night vision Visible – you can see this presentation Ultraviolet – tanning X-ray – see broken bones Gamma – kill cancerous cells

Sound Sound is a mechanical wave (requires a medium to travel) and a compressional wave (molecules colliding) The medium sound travels through are molecules when they collide

Sound Sound is produced when an object vibrates. When an object vibrates it exerts a force on the surrounding air Loudness of a sound is recorded in decibels As a sound gets louder, the amplitude of the wave increases

Sound The moving air mass carries the sound of the vibration to your ear. The air is the MEDIA that it travels through. Medium is what the wave travels through (ex. solid, liquid, gas) NO MEDIUM NO SOUND!!!!

The Echo An echo is when a sound wave hits a hard surface and bounces back, causing you to hear the sound a second time Sonar uses echoes. It is a measure of how long it takes the echo to return to the source of the sound. Sonar can tell you how far an object is from you.

Speed of Sound The speed of sound is different depending on the medium it travels through

Speed of Sound Sound travels at different speeds through different medium The more dense a material the faster sound travels 346 m/s in warm air 5,000 m/s in aluminum 3,240 m/s in gold

Speed of Sound Sound travels better through high-density materials The closer the molecules are together, the faster they can collide and transfer energy

Light EM wave that travels transversely (up and down motion) Primary colors are red , green and blue White light is made up of all colors Black is the absence of color

Light (cont.) We see colors because objects reflect light If you see a color, that specific color is being reflected while the rest are being absorbed (taken in) by the medium White reflects all colors Black absorbs all colors

What is Light? It is a transverse wave that carries energy It is a small part of the ElectroMagnetic Spectrum Because it is part of the electromagnetic spectrum, it can travel through a vacuum (space)

How do you see the things around you?

Without light, there is no sight!

Light REFLECTS off of objects.

How we see When light strikes an object the light bounces off of the object and then into our eye. For example, the light from the this projector hits the screen and then is reflected to your eye.

Transparent, Translucent, Opaque

Opaque, Translucent, Transparent Objects that do not let light pass through them are opaque. Ex. Walls, your desk, the science book Objects that let light pass clearly through them are transparent. Ex. Windows, plastic wrap, eye glass lenses Objects that let only some light pass through are translucent. Ex. waxed paper, frosted glass

COLORS The suns light might appear white, but it is a mixture of colors. White light is produced when you mix the colors of the rainbow together.

Light Color Mixing The primary colors of light are RED, BLUE and GREEN

So why do we see different colors? When white light hits an object some of it may be absorbed by the object while the rest of the light is reflected. The colors we see are the reflected colors.

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