Illumination
• Ray Model of Light
• Luminous source
• Illuminated source
• Opaque
• Transparent
• Translucent
• Luminous Flux
• Illuminance
• Speed of light, c
• Inverse square law
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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).
Polarization
• Malus’s Law
• Intensity
• Wavelength – Decrease – objects moving toward each other
– Increase – objects moving away from each other
22 1 cosI I
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PE
r
obs
v
c
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
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