3Sound Waves Produced from vibrating particles Particles “bump” into each other to transfer the energy through the mediumTravel in longitudinal wavesTravel in all directions (like a circle)Can travel through solids, liquids, and gasesFaster in solids and liquids than gasesCannot travel in a vacuum(through empty space)
4Sound Examples Percussion instruments have vibrating membranes String instruments have vibrating stringsWoodwinds have vibrating reedsBrass instruments vibrating lipsYour vocal cords are two thin elastic bands that vibrateSay “ahhhhh” and touch your throat. Feel them?
5Notice: High frequencies have shorter wavelengths. PitchHow high or low a sound isDetermined by frequency of the sound waveFrequency is determined by how quick or slow the particles vibrateSlow VibrationLow FrequencyLow PitchQuick VibrationHigh FrequencyHigh PitchNotice: High frequencies have shorter wavelengths.
6IntensityDetermines the “loudness” of the soundIntensity decreases with distance from the sources as it spreads outDepends on the amplitude of the soundHigher amplitudes produce louder soundsLouderSofterNotice: The wavelength and frequency are the same. Only amplitude changed.
7Hearing Sound: The Ear3 bones: hammer, anvil, and stirrupSound causes your eardrum to vibrate. The eardrum vibrates differently for each sound.The bones of your ear begin to vibrate, beginning with the hammer, moves to the anvil, and finally the stirrupEardrum
8Hearing Sound: The EarCochleaOuter EarThe sound energy passes to the inner ear. This causes the fluid in the cochlea to move.The nerves then carry the message to the brain. Your brain then tells you what the sound is.Inner Ear
9Producing Sound: The Vocal Chords Air from the lungs flows through the windpipe and into the voice box (where the vocal cords are).Then the air pushes the vocal cords apart making them vibrate.3. The vibrations create a series of sound waves that exit through your mouth.
10Producing Sound: The Vocal Chords The change of shape of the vocal cords changes the sound and its pitch.If you can’t talk because of a cold or laryngitis, it is because your vocal cords are swollen and inflamed.
11More About Sound Sonar- Sound Navigation And Ranging Ultrasound Determine distance by measuring the time it takes for sound waves to be reflected backUsed by ships, submarines, and batsUltrasoundUse echos to produce images called sonograms of inside the body without performing surgery
12Did You Know?Sound waves that are reflected off boundaries are called “echos.”Sound travels 4 times faster in water than air.Any frequency of sound below the range of human hearing (20 Hz) is called Infrared sound.Any frequency of sound above the range of human hearing (20, 000 Hz) is called Ultrasound.
13Doppler EffectChange in frequency of a wave due to relative motion between source and observer.A sound wave frequency change is noticed as a change in pitch.
15Light Waves “Dual natured” Travel in transverse waves Travel in straight lines in all directionsCan travel through some solids, liquids, and gasesSlow down when traveling through a mediumCan travel in a vacuum (through empty space)Consist of changing electric and magnetic fields in space
16Where does light come from? Our major light source:the Sun
18Two Models of Light Wave Model Stream of Particles Model Transverse waves that do not need a mediumExplains why light can reflect, refract, or diffract, interfer with one another, and produce standing wavesStream of Particles ModelPhotons- packets of light, localized energyExplains why blue light can knock electrons off a metal plate but red light cannot, and why light can travel without a mediumThe model used depends on the situation
19Energy and Frequency Energy of light is proportional to frequency Higher frequency = more energy
20The Speed of Light In a vacuum, all light travels at the same speed 3 x 108 m/s = 186,000 miles/secSymbol “c”Light is the fastest signal in the universeAlso can travel through transparent mediumsAir, water, and gasTravels slower when passing through a mediumMore dense = slower speed
21Intensity Determines the “brightness” of light Intensity decreases with distance from the sources as it spreads outDepends on amount of light (number of photons or power passing through)
23How Light TravelsLight rays travel in straight lines from the light source.When it hits an opaque object, some light is absorbed and the rest reflects off.If the object is transparent, light rays pass through it easily.If the object is translucent, some light can pass through, but the rest of the light will be reflected.
24The ‘angle of reflection’ is always equal to the ‘angel of incidence’. offAngle of incidenceAngle of reflectionThe ‘angle of reflection’ is always equal to the ‘angel of incidence’.
25Only red light is reflected Seeing ColorThe colour an object appears depends on the colours of light it reflects.For example, a red book only reflects red light:HomeworkWhitelightOnly red light is reflected
26ColorsWhite light can be split up to make separate colours. These colours can be added together again.The primary colours of light are red, blue and green:Adding blue and red makes magenta (purple)Adding blue and green makes cyan (light blue)Adding red and green makes yellowAdding all three makes white again
27A white hat would reflect all seven colours: A pair of purple trousers would reflect purple light (and red and blue, as purple is made up of red and blue):Purple lightA white hat would reflect all seven colours:Whitelight
28Refraction Waves travel different speeds in different mediums When waves change mediums, their speed changes causing the waves to bend
29DiffractionlightsourcelightsourceLight rays travel in straight lines, radiating out from the light source.If rays are blocked by an opaque object a shadow forms where the light cannot reach.If the light source is moved closer to the object, more light is blocked and a larger shadow is formed.
30Shadows Looking North, the Sun appears to rise in the East... 12amLooking North, the Sun appears to rise in the East...2pm10amThe position of the Sun effects the position and length of the shadows created.9am3pm8am4pm6am7pmThanks to this natural phenomenon a sundial is able to tell us the time, as long as it is a sunny day!...and travel across the sky until it sets in the West.
31Seeing Light: The EyeLight coming from, (or reflecting off) objects enters the eye through the cornea then the pupil.It is focused clearly by the lens on to the retina.The light sensitive cells of the retina gather information about patterns of light and dark, color and movement and send it through the optic nerve.
32Seeing Light: The EyeInformation entering the brain through the optic nerve, is then transmitted through more nerve pathways to the visual cortex.Here the patterns of light and dark, colour and movement are interpreted.The brain, based on past experience, can then understand what it ‘sees’.
33More about Light Sunlight contains ultraviolet and infrared UV will burn you, IR warms youX-rays and gamma rays are high frequency light waves used in medicineMicrowaves are used in cooking and communication (mobile phones)Radio waves are used in communication and radarRadar: Radio Detection And RangingUses reflected radio waves to determine velocity and location
34Did You Know?Rainbows are the refraction of white light through water droplets that reflect them back in the air.Fiber optics operate on total internal reflection.The interference of light waves create the rainbow swirls on bubbles.The light we see from the sun is 8 minutes old. It takes light 8 minutes to travel from the sun to Earth even at its fast speed.