Science 8: Light Waves
www.youtube.com/watch?v=fm__GAlrBuQ Visible Light •The part of the electromagnetic spectrum, between infrared and ultraviolet, that is visible to the human eye. •Shorter waves – higher frequency and energy •Longer waves – lower frequency and energy Visible Light Spectrum •Produced when light passes through a prism, slowing the wavelength into each separate color. •ROY G. BIV - red, orange, yellow, green, blue, indigo, violet Colors •We see these waves as the colors of the rainbow. •Each color has a different wavelength and frequency. •Red has the longest wavelength and shortest frequency •Violet has the shortest wavelength and highest frequency. •Seen together, they make white light. Visible Objects •For an object to be visible it must produce its own light or reflect light. •Produces own light - Sun, candle, flashlight •Reflects light - Moon, mirror, glass Vocabulary •Opaque – A material that reflects or absorbs all of the light that strikes it. (wood, metal, cardboard) •Transparent – transmits light (glass, water, air) •Translucent – scatters light as the light passes through (wax paper, frosted glass) How light travels •Light travels in straight lines. •This straight line motion can be: •Reflected •Diffused •Refracted Absorbed Reflection •Occurs when parallel rays of light hit a smooth surface. •All the rays are reflected at the same angle. •Law of reflection: the angle of reflection equals the angle of incidence. •Angle of incidence - measure of the angle of a ray to the surface normal (90o to the surface) Diffusion •When parallel rays of light hit a bumpy surface. •Each ray obeys the law of reflection, but each ray hits the surface at a different angle. The light is scattered. Refraction •When light waves enter a new medium at an angle, their speeds changes. •The change in speed causes them to bend, or change direction. •Index of Refraction – a measure of how much a ray of light bends when it enters that material Lenses •When light traveling in straight parallel lines passes through an object that is curved like a lens, the light is refracted at different angles. •Convex or converging lenses bend light toward a central focal point. •Concave or divergent lenses bend light outward away from a focal point. Absorption •Light does not pass through or reflect from material, but remains in the material as energy. •What happens to the black surface? Color of objects •Color – Objects reflect colored light that is not absorbed. •We see objects color as the reflected color. Colors of Light •Primary •Red, Blue and Green •When combined in equal amounts, primary colors produce white light. •If combined in varying amounts, they can produce any other color. •Secondary •Yellow, Cyan and Magenta •Primary colors combined in varying amounts •Complementary - form when a primary color and a secondary color combine to make white. •Yellow and blue = white •Y + B = W or R + G + B = W Brightness •A relative expression of the intensity of the energy output of a visible light source •Brightness is determined by the light wave’s amplitude. •The greater the amplitude, the brighter the light. •Distance from light source also affects brightness. Comments are closed.
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Erik E. Mason
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