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Sound and Light

The Nature of

Light

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Constructive and Destructive Interference

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Light Can Be Modeled As a Wave

Light Diffracts like a waveLight also reflects and refracts

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Max Planck and Albert Einstein

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

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Photon

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.

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Atoms Emit Energy As Photons

Absorbs Energy

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Sometimes Light is modeled as a Stream

of ParticlesExplains why light can travel through the vacuum of spaceLight can knock electrons off a metal plate

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Light Has a Dual Nature

DualityDifferent characteristics depending on the situationScientists use different models depending on what they are studying

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Photon Self-identity Problems

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Energy of Light Is Proportional to

FrequencyLight is a form of energy.The energy, E, of a photon is E = h, Where h is Planck's constant and is the frequency of the light.

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The Speed of LightIn a vacuum it is called ‘c’Depends on the medium

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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

Earth Moon 376,280km 233,810 miles

1 ¼ seconds

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Earth

Sun 150,000,000 km (93,000,000 miles)

8 1/3 minutes

Earth

Proxima Centauri, the nearest star 41,000,000,000,000 km

4 1/3 years

Where you are:

Source of light:

Time to get there:

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The Brightness of Light Depends on the

Intensity

The rate at which light energy flows through a given area of space is referred to as its intensity.

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The Brightness of Light Depends on the

IntensityLight waves spread out spherically from the sourceTherefore intensity will drop as distance increases

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Exploring the Electromagnetic

Spectrum

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System that uses reflected radio wavesDetermine distance, location, shape and speed

Radar

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Sound and Light12.3

Reflection and Color

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Light Can Be Modeled As a Ray

Light ray is a model of lightRepresents light traveling through space in an imaginary straight line

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When Light Rays Reflect off a Smooth Surface, They Are

Reflected in the Same Direction.

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When Light Rays Reflect off a Rough Surface, They Scatter in Many Different Directions.

Diffuse reflection

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The Law of ReflectionStates that when light rays reflect off a surface the angle of incidence equals the angle of reflection.'

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The Law of Reflection

Ө = Angle of

incidence

Ө’ = Angle of

reflection

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NormalThe theoretical line perpendicular to the surface where light hits a mirror.

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Virtual ImageAn image that results from an apparent path of light rays

Appears behind a mirror

Or in front of a lens

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Flat Mirro

r

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Real Image

Light rays really exist at the point where the image appears.

Appears in front of a mirror.

Or through a lens.

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Concave and Convex Mirrors

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Can create real images

Concave Mirrors

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Fun House Mirrors

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Reflection of Green Light by Leaves

Life Science, Holt Science and Technology, California edition, Holt Rinehart and Winston, San Francisco, 2001

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Seeing ColorObjects have color because they reflect certain wavelengths of lightThe object absorbs all the other colorsYour brain interprets each wavelength as color

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Colored Filters

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You look at a red tulip, with green leaves,

under green light. What would you see?

A black flower with green leaves

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The Primary Colors of Light and Pigment

Light PigmentAdditive Subtractive

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Primary Colors of Printing

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What are the True Colors?

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Sound and Light 12.4

Refraction, Lenses and

Prisms

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RefractionBending of light raysFrom one medium to anotherDue to changing speeds

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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.

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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

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Refraction in the Atmosphere

Creates miragesAre a virtual imageHeat leads to diffraction that bends the light toward the sky

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Total Internal ReflectionLight enters one end of a fiber optic cable and exits the other endComplete reflectionBetween two mediumsAngle of incidence exceeds the critical angle

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Convex Lens

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Convex Lens

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Convex Lens

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Concave Lens

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diverging lensesConcave Len.It bends light outward and can only create a virtual image.

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The Eye

the cornea is responsible for the largest percentage of light refraction

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Camera

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Prism

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DispersionThe effect in which white light separates into different colorsDue to changes in wave speed of the different colors

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White Light contains all the colors of the

rainbow

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Rainbows

Caused by dispersionAnd internal reflection

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Study Guide

Pitch of a sound  CorneaHarmonics,  Amplitude Law of reflection  Real image, virtual imageDiverging lens  Electromagnetic spectrum

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Intensity, sound and lightResonance particle and wave models of light  energy of a photon Diffuse reflection  Color, frequency Refraction, normal total internal reflection.  Prism and differences in wave speed

 

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6. An orange looks orange because ita. reflects orange light and absorbs other colors.

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7. When light moves from a material in which its speed is higher to a material in which its speed is lower, it isa. bent toward the normal. 28. 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

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9. Which structure within eye?

b. the cornea is responsible for the largest percentage of refraction of light

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12. The unique sound quality of a clarinet or a violin is caused by thec. relative intensity of different harmonics in each note.

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18. A virtual image caused by reflection of light in the atmosphere is called

d. a mirage.

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10. White light breaks up into different colors when it passes through a prism because ofa. differences in wave speed.

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