10-11 (Light)

10-11 (Light) - o Rougher surface(matte surface •...

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LIGHT What is light? o Light is a form of electromagnetic radiation that behaves in three ways: As a ray that travels at high speed in a straight line (geometric optics) As discrete packets or particles of energy (photons) that can be counted individually at low light levels (quantum mechanics) As a wave vibrating at a specific frequency. The wave properties of light explains its behavior at very fine scales (physical optics) When light interacts with a surface, it can do a number of different things o If not entirely opaque, it can travel through (transmission) o If density much different from air medium, the transmission won’t be direct (it will be refracted) o Light can be absorbed (light energy is converted into heat/thermal energy) o Light can be reflected Types of reflection: Specular – all light waves are reflected in the same direction o Surfaces tend to be glossy Diffuse – not all light waves will be reflected in the same direction
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Unformatted text preview: o Rougher surface (matte surface) • Refraction =wavefront retardation • Visible light: 400 – 700 nm • Three aspects of light important for vision o Intensity Luminance = physical quantity/measurement • The amount of energy emitted or reflected by an extended light source • Expressed in candelas per square meter • 1 candela = the amount of light emitted by a single burning candle o Contrast A measure of the difference between the highest luminance and the lowest luminance in a scene, so it represents relative rather than absolute luminance. • C=(L max – L min )/(L max +L min ) The reflectance of a surface is the proportion of incident light that it reflects. Contrast in natural scenes depends on surface reflectance -- the contrast between a piece of coal and a sheet of paper is constant at different luminance levels. o Wavelength...
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This note was uploaded on 01/09/2011 for the course PSYC 225 taught by Professor Staff during the Fall '10 term at UNC.

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10-11 (Light) - o Rougher surface(matte surface •...

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