Sound and Light 1 The Nature of Light

Waves & Sound A. Waves 1. The nature of waves a. A wave is a rhythmic disturbance that transfers energy. b. All waves are made by something that vibrates.

B. Sound 1. Energy is transferred from particle to particle through matter. 2. How we hear a. Outer ear collects sound. b. Middle ear amplifies sound. c. Inner ear converts sound.

 The ear is a very sensitive organ.  It senses vibrations in the air then amplifies them and transmits signals to the brain

3. Properties of sound a. Intensity and loudness 1) Intensity depends on the energy in a sound wave. 2) Loudness is human perception of intensity. 3) Loudness is measured on the decibel scale. b. Frequency and pitch 1) High frequency means more vibrations hitting the ear. 2) Pitch is how high or how low a sound seems to be. 3) Healthy humans can hear from 20 Hz to 20,000 Hz 4) We are most sensitive from 440 Hz to 7,000 Hz.

 This all depends on how the particles can transmit the compressions and rare factions of sound waves  The speed of sound depends on the medium

 The loudness of a sound depends partly on the energy contained in the sound wave.  The intensity of a sound wave describes the rate at which a sound wave transmits energy through a given area of the medium.  The greater the intensity of a sound, the louder the sound will seem

 The air column in a clarinet, however vibrates at its fundamental frequency and at certain whole number multiples of that frequency called harmonics.  The sound produced by the guitar will be the loudest when the forced vibrations cause the body of the guitar to vibrate at a natural frequency called resonance.

a) Threshold of hearing (0 db) b) Threshold of pain (120 db)

5) Ultrasonic sound has a frequency greater than 20,000 Hz. a) Dogs (up to 35,000 Hz) b) Bats (over 100,000 Hz) c) Medical diagnosis 6) Infrasonic sound has a frequency below 20 Hz; they are felt rather than heard (earthquakes, heavy machinery).

c. Speed of sound 1) 332 m/s in air at 0 C. 2) Changes by 0.6 m/s for every Celsius degree from 0 C. 3) Subsonic – slower 4) Supersonic – faster than sound (Mach 1 = speed of sound) 5) Sonic Boom (skip to1:35)pressure cone)Sonic Boom

d. The Doppler effect – the change in pitch due to a moving wave source. 1) Objects moving toward you cause a higher pitched sound. 2) Objects moving away cause sound of lower pitch. 3) Used in radar by police and meteorologists and in astronomy.

4. Musical sound a. Noise has no pattern. b. Music has a pattern and deliberate pitches. c. Sound quality describes differences of sounds that have the same pitch and loudness. d. Every instrument has its own set of overtones. e. Beats are pulsing variations of loudness caused by interference of sounds of slightly different frequencies.

5. Uses of sound a. Acoustics – the study of sound. Soft materials dampen sound; hard materials reflect it (echoes and reverberations). b. SONAR – Sound Navigation and Ranging (echolocation). c. Ultrasound imaging d. Kidney stones & gallstones.

 A sonar works by measuring the time it takes for sound waves to be reflected back from a surface.  Ultra sound imaging is used in medicine.  Using sonograms, doctors can safely view organs inside the body without having to perform surgery.  Sonograms can be used to diagnose problems, to guide surgical procedures, or even to view unborn fetusus.

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 Light Diffracts like a wave  Light also reflects and refracts Sound and Light 18

 Nobel prize winners in physics  Discovered that light, which usually travels in waves, sometimes behaves as if it were made up of a stream of small quantities, or quanta, of energy Sound and Light 19

 Small unit of light energy or electromagnetic radiation. “Packets”  No mass, bundle of energy.  The energy, E, of a photon is calculated using the equation E = h ,  Where h is Planck's constant and  is the frequency of the light. Sound and Light 20

Sound and Light 21 Absorbs Energy

 Explains why light can travel through the vacuum of space  Light can knock electrons off a metal plate  Duality  Different characteristics depending on the situation  Scientists use different models depending on what they are studying Sound and Light 22

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 In a vacuum it is called ‘c’  Depends on the medium Sound and Light 24

Sound and Light 25 Where you are: Source of light: Time to get there: Home Plate Outfield fence 125m (410ft) ½ of a millionth of a second Soccer goal Other goal 100m (328ft) 1 / 3 of a millionth of a second EarthMoon 376,280km 233,810 miles 1 ¼ seconds

Sound and Light 26 EarthSun 150,000,000 km (93,000,000 miles) 8 1 / 3 minutes EarthProxima Centauri, the nearest star 41,000,000,000,000 km 4 1 / 3 years Where you are: Source of light:Time to get there:

 The rate at which light energy flows through a given area of space is referred to as its intensity.  Light waves spread out spherically from the source  Therefore intensity will drop as distance increases Sound and Light 27

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 System that uses reflected radio waves  Determine distance, location, shape and speed Sound and Light 29

Reflection and Color Sound and Light 31

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Sound and Light 33 Diffuse reflection

 States that when light rays reflect off a surface the angle of incidence equals the angle of reflection. Sound and Light 34 Ө = Angle of incidence Ө ’ = Angle of reflection

 The theoretical line perpendicular to the surface where light hits a mirror. Sound and Light 35

 An image that results from an apparent path of light rays  Appears behind a mirror  Or in front of a lens REAL IMAGE:  Light rays really exist at the point where the image appears.  Appears in front of a mirror.  Or through a lens. Sound and Light 36

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 Can create real images Sound and Light 38

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 Objects have color because they reflect certain wavelengths of light  The object absorbs all the other colors  Your brain interprets each wavelength as color Sound and Light 40 Reflection of Green Light by Leaves

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 A black flower with green leaves Sound and Light 42

Sound and Light 43 Light Pigment AdditiveSubtractive

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Refraction, Lenses and Prisms Sound and Light 47

 Bending of light rays  From one medium to another  Due to changing speeds Sound and Light 48

 When light moves from a material in which its speed is higher to a material in which its speed is lower, it is…  Bent toward the normal. _________________________________  If a light moves from a material in which its speed is lower to one in which its speed is higher,  The ray is bent away from the normal Sound and Light 49

 Creates mirages (Aurora Borealis)  Are a virtual image  Heat leads to diffraction that bends the light toward the sky Sound and Light 50

 Light enters one end of a fiber optic cable and exits the other end  Complete reflection  Between two mediums  Angle of incidence exceeds the critical angle Sound and Light 51

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 Concave Lens  It bends light outward and can only create a virtual image. Sound and Light 56

Sound and Light 57 the cornea is responsible for the largest percentage of light refraction

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 The effect in which white light separates into different colors  Due to changes in wave speed of the different colors  Rainbows are Caused by dispersion & internal reflection Sound and Light 60

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Sound and Light 62 Pg , 30, 38 Pg Pg , 25, 37 Pg Copy the question and Complete answers