what’s wrong with this? drill #34 quote: persistent work triumphs. ~virgil objective: math taks...

What’s wrong with this?

Drill #34

Quote: Persistent work triumphs. ~Virgil

Objective: Math TAKS

Sound and Light

WAVES: SOUND & LIGHT

Waves carry energy from one place to another

© 2000 Microsoft Clip Gallery

Sound... ...a longitudinal wave in air caused by a

vibrating object. Produced by tiny fluctuations of air

pressure Carried through air at 345 m/s (770

m.p.h) as compressions and rarefactions.

wavelengthcompressed gas

rarefied gas

Waves in air can’t be transverse, because the molecules are not bound to each other.

Air molecules can only bump into one another.

Why is Sound Longitudinal?

Origin of Sound infrasonic

frequencies < 20 Hz ultrasonic

frequencies > 20,000 Hzhuman hearing range

frequencies between 20 Hz and 20,000 Hz

The frequency of an audible sound determines how high or low we perceive the sound to be. (pitch)

greater frequency = greater the pitch.

Origin of Sound (Cont.)

Nature of Sound in Air and Solids

Speed of sound in air is related to the frantic motions of molecules as they jostle and collide.

Solids have faster sound speeds due to close molecule proximity & molecular bonding. don’t have to rely on atoms to traverse gap spring compression can (and does) travel faster

than actual atom motion.

Medium sound speed (m/s)

air (25C) 345

water 1490

gold 3240

brick 3650

wood 3800–4600

glass 5100

steel 5790

aluminum 5100

Example Sound Speeds

What is the approximate distance of a thunderstorm when you note a 3 second delay between the flash of the lightning and the sound of the thunder?

Answer: 3 seconds 340 meters/second

= 1020 meters

Sample Problem

DOPPLER EFFECT …a frequency shift that is the result of

relative motion between the source of the waves and the observer.

Doppler with Sound

Some applications of the Doppler effectSome applications of the Doppler effect

Doppler flow meter measures speed of blood flow in blood vessels. A transmitter generates high frequency (~5MHz) “sounds” that move through the body and bounce off red blood cells. The motion of the blood cells cause a Doppler shift in the sound waves (in the hundreds of Hz range), that can be measured by a receiver.

Ultrasound, sonar, echolocation and seismic exploration are all ways in which machines or animals can image the surroundings using sound waves. A sound wave is emitted, bounces off reflective surfaces in the environment, and the reflected signals are observed. The time delay between transmission and reception of the wave is related to the distance to the reflecting surface, transmission and reflection properties of the media, etc., and this information can be used to reconstruct an image of the surroundings.

ultrasound image of a fetus sonar image of a shipwreck in Lake Ontario

Some applications of Doppler effect

Doppler radar used in weather forecasting to detect local velocities in a storm system: same principle as with the Doppler effect in sound waves, only here the frequency shift is in radio waves bouncing off moving water droplets in a storm.

Some applications of Doppler effectSome applications of Doppler effect

Radar

True Velocity

Tangential Velocity

Radial Velocity

Some applications of Doppler effectSome applications of Doppler effect

LIGHT & USES: Diffraction

Diffraction – Bending of waves around the edge of a barrier. New waves are formed from the original. breaks images into bands of light & dark and colors.

Refraction – Bending of waves due to a change in speed through an object.

EVALUATION: State Standards

Waves carry energy from one place to another

Identify transverse and longitudinal waves in mechanical media such as spring, ropes, and the earth (seismic waves)

Solve problems involving wavelength, frequency, & speed.

.


Radio waves, light, and x-rays are different wavelength bands in the spectrum of electromagnetic waves whose speed in vacuum is approximately 3x10 m/sec

Sound is a longitudinal wave whose speed depends on the properties of the medium in which it propagates.


Identify the characteristic properties of waves: Interference Diffraction Refraction Doppler Effect Polarization.

NATURE OF WAVES

Waves (Def.) – A wave is a disturbance that transfers energy.

Medium – Substance or region through which a wave is transmitted.

Speed of Waves – Depends on the properties of the medium.


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



Electromagnetic Waves

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

Speed in Other MaterialsSlower 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

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

Orange, Yellow, Green, Blue, Indigo, & Violet.

Largest to Smallest Wavelength.


Invisible SpectrumRadio Waves

Def. – Longest wavelength & lowest frequency.

Uses – Radio & T.V. broadcasting.


Modulating Radio Waves

Modulation - variation of amplitude or frequency when waves are broadcast AM – amplitude modulation

Carries audio for T.V. BroadcastsLonger wavelength so can bend around hills

FM – frequency modulation Carries video for T.V. Broadcasts


Short Wavelength Microwave

Invisible Spectrum (Cont.)Infrared Rays

Def – Light rays with longer wavelength than red light.

Uses: Cooking, Medicine, T.V. remote controls


Invisible spectrum (cont.).Ultraviolet rays.

Def. – EM waves with frequencies slightly higher than visible light

Uses: food processing & hospitals to kill germs’ cells

Helps your body use vitamin D.


Invisible Spectrum (Cont.)X-Rays

Def. - EM waves that are shorter than UV rays.

Uses: Medicine – Bones absorb x-rays; soft tissue does not.

Lead absorbs X-rays.


Invisible spectrum (cont.)Gamma rays

Def. Highest frequency EM waves; Shortest wavelength. They come from outer space.

Uses: cancer treatment.

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. Prisms – Glass that bends light. Different

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

Color of Light Transparent Objects:

Light transmitted because of no scattering Color transmitted is color you see. All

other colors are absorbed. Translucent:

Light is scattered and transmitted some. Opaque:

Light is either reflected or absorbed. Color of opaque objects is color it reflects.


Color of Light (Cont.)

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.


LIGHT & ITS USES - 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.

LIGHT & ITS USES: Reflection Vocabulary

Enlarged – Image is larger than actual object.

Reduced –Image is smaller than object.

Erect –Image is right side up. Inverted – Image is upside down



Light & Its Uses: Mirrors

Reflection VocabularyOptical Axis – Base line through the

center of a mirror or lensFocal Point – Point where reflected or

refracted rays meet & image is formedFocal Length – Distance between

center of mirror/lens and focal point


LIGHT & ITS USES: Mirrors Reflection & Mirrors (Cont.)

Convex MirrorCurves outward, thicker in center than

edgesConverges light rays (brings together)

Use: Rear view mirrors, store security… Concave Lenses –

Lens that is thicker at the edges and thinner in the center.

Diverges light rays All images are erect and reduced

CAUTION! Objects are closer than they appear!© 2000 Microsoft Clip Gallery

LIGHT & USES: Optical Instruments

LASERSAcronym: Light Amplification by

Stimulated Emission of RadiationCoherent Light – Waves are in

phase so it is VERY powerful & VERY intense.

LIGHT & USES: Optical Instruments

LASERS Holography – Use of Lasers to create

3-D images Fiber Optics – Light energy

transferred through long, flexible fibers of glass/plastic

Uses – Communications, medicine, t.v. transmission, data processing.

what’s wrong with this? drill #34 quote: persistent work triumphs. ~virgil objective: math taks...

Documents

sound waves

nature of sound

sound lightwaves

audible sound

solidsspeed of sound

longitudinal waves

faster sound speeds

example sound speeds