LightIllumination

Illumination

• Ray Model of Light

• Luminous source

• Illuminated source

• Opaque

• Transparent

• Translucent

• Luminous Flux

• Illuminance

• Speed of light, c

• Inverse square law

24

PE

r

Ray Model of Light

• A ray that travels in a straight path– Does not account for diffraction

• Can only be altered by an object in the path

• Used to model interactions with matter• Ray optics or geometric optics

Pg 431-438

Ray Model of Light

• Sources of light– Luminous source emits light

– Illuminated source reflects light

• Luminous sources– Examples

• Illuminated sources can be– Opaque (does not transmit light. May

reflect)

– Transparent (transmits light. May reflect)

– Translucent (transmits light, but not clearly. May reflect)

Ray Model of Light

• Luminous flux, P– Rate at which light energy is emitted from

a luminous source

– Units = lumen (lm)

– All of the light

• Luminous intensity– Units = candela (cd)

– Luminous flux divided by 4π

Ray Model of Light

• Speed of light– c = 3.0 x10^8

• Inverse square law– x=1/(y^2)

– When y increases, x decreases by a square factor.

• Reflection– Ray that returns (bounces) off of a

boundary (may changes directions).

• Refraction– Ray that is transmitted through a

boundary (may changes directions).

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Light

The Wave Nature of Light

The Wave Nature of Light

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Polarized Light

Polarization

• Malus’s Law

• Intensity

• Wavelength – Decrease – objects moving toward each other

– Increase – objects moving away from each other

22 1 cosI I

24

PE

r

obs

v

c

Equation Review

0

c

f

obs

v

c

1obs

vf f

c

Speed of light as a constant

Home work

• Describe the similarities and differences between the velocity of sound (v=fλ) and the velocity of light (c=fλ). – Hint: Pg 445

• Describe the similarities and differences between the Doppler effect as it applies to sound vs. light.– Hint: Pg 407 & 446

The Wave Nature of Light

• Diffraction

• Primary Color

• Secondary Color

• Complementary Colors

• Primary Pigment

• Secondary Pigment

• Polarization

• Malus’s Law

• Clara!

22 1 cosI I

0

c

f

1obs

vf f

c

obs

v

c

The Wave Nature of Light

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Elements