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Light is electromagnetic radiation capable of
affecting the sense of sight. |
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What is the source ? |
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How does it get from point A to B ? |
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Is it affected by the medium ? |
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What happens when it strikes an object ? |
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Observations of light |
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Rectilinear propagation (straight line motion) |
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Diffraction - the bending of light around an
object |
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Reflection |
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Refraction |
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how is light affected by the medium ? |
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Energized (accelerated) charges will radiate
electromagnetic waves. |
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Electromagnetic waves are pushed by the electric
and magnetic fields oscillating perpendicular to each other, |
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Broad range of frequencies and wavelengths all
travelling at the same speed (c = 3 x108 m/s) |
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A light beam may cause electrons to jump from
one metallic surface to another |
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supports the particle theory |
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Light is radiant energy transported in photons
carried along by a wave field |
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Photons are “packets of energy” released as
electrons give off energy they have gained from an outside source |
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the energy is directly related to the frequency |
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Energy is directly related to frequency |
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Primary colors |
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red, blue and green for light |
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red blue and yellow for pigments |
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Additive vs subtractive |
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secondary colors |
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complimentary colors |
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The brightness of a light is the visual
sensation. This is a subjective value but it can be measured. The
scientific measurement is called the luminous flux. |
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The luminous flux is the portion of the radiant
power emitted from a light source, which we can see. |
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It is measured in lumens. |
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The intensity of a light source depends on how
the radiant power (flux) is distributed. |
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The three dimensional (solid) angle over which
the light is dispersed can make the same source appear as bright as a spot
light or as dim as an bare light bulb. |
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Light intensity is measure in candles. |
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How bright an object appears depends on the
amount of surface area the radiant power (flux) is dispersed upon. |
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The number of lumens (flux) per square meter is
called the lux. (A lumen per square foot is referred to as footcandle) |
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Notes