light chapter 13. ch13 sec 1 the behavior of light
TRANSCRIPT
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LightChapter 13
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Ch13 Sec 1The Behavior of Light
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Light and Matter
• Objects must reflect light to be seen.– Opaque materials do not allow light to pass
through them; they only absorb and reflect light
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Light and Matter
• Objects must reflect light to be seen.– Opaque materials do not allow light to pass
through them; they only absorb and reflect light– Some light passes through translucent materials.
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Light and Matter
• Objects must reflect light to be seen.– Opaque materials do not
allow light to pass through them; they only absorb and reflect light
– Some light passes through translucent materials.
– Transparent materials allow almost all light to pass through them; only a little light is absorbed and reflected.
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Reflection of light
• Reflection of light – a light wave strikes an object and bounces off.
• Law of Reflection – angle at which light strikes a surface is the same as the angle at which it is reflected
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Regular Reflection
• Regular reflection – reflection of light waves from a smooth surface
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Diffuse Reflection
• Diffuse reflection – reflection of light waves from a rough surface
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Refraction of Light
• Refraction of light - change in the speed of a light wave when it passes from one material to another
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Index of refraction
• The index of refraction indicates how much a material reduces the speed of light; the more light is slowed, the greater the index of refraction.
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Prisms
• Separate white light into visible spectrum based on light wavelength
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Rainbows
• Caused by water droplets refracting wavelengths of sunlight
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Chapter 13 Section 2Light and Color
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Colors…• Colors are determined by wavelength
of light an object reflects.–White objects reflect all colors of
visible light.–Black objects absorb all colors of visible
light.
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Colors…• Colors are determined by wavelength of light an
object reflects.– White objects reflect all colors of visible light.– Black objects absorb all colors of visible light.
– Filter – is a transparent material that absorbs all colors except the color or colors it transmits• Filters can make
objects appear to be different colors.
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Seeing Color
• Light enters the eye and is focused on the retina.– Retina – made up of two types of cells that absorb
light
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Seeing Color…• Light enters the eye and
is focused on the retina.– Retina – made up of two
types of cells that absorb light• Cones – distinguish colors
and detailed shapes; most effective in daytime vision
• Rods – sensitive to dim light; most effective in nighttime vision
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Colorblindness Tests
Test Name: Ishihara Test
Colorblind sees:yellow square
Normal color:yellow square &
faint brown circle
Colorblind sees:the number 17
Normal Color sees:the number 15
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Colorblindness
• Results from when one or more sets of cones do not function properly
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Mixing colors•Pigment – colored material
that absorbs some colors and reflects others
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Mixing colors
• Pigment – colored material that absorbs some colors and reflects others
• Primary colors of light – Red, Green, and Blue• Primary colors of pigment – magenta, cyan, and yellow
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Mixing colors• Pigment – colored material that absorbs some colors and reflects others• Primary colors of light – Red, Green, and Blue• Primary colors of pigment – magenta, cyan, and yellow
• Primary colors of light are additive colors – combine to form white
• Primary colors of pigments are subtractive colors – combine to form black, the absence of reflected light
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Producing LightChapter 13 Section 3
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Incandescent lights
• Hot tungsten wire glows; gives off light and heat
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Fluorescent lights
• Electrons collide with gas atoms, releasing ultraviolet radiation absorbed by phosphorus lining the bulb; gives off light
Why are these better than Incandescent bulbs?– Less energy used– longer lasting
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Neon lights
• Tubes filled with gas (usually neon) produce light from electron collisions; different colors can be made by adding different gases
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Sodium-vapor lights
• Heated neon gas glows and warmth turns sodium into a vapor, producing a yellow-orange glow; used for outdoor lighting.
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Tungsten-halogen lights
• Have a filament and gas enclosed in a glass bulb to produce intensely bright light
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Lasers
• Light beam produced when identical atoms send off identical light waves; can be made from gases, liquids, or solids
• FYI – LASER – Light Amplification by Stimulating Emissions of Radiation
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Lasers• Light beam produced when
identical atoms send off identical light waves; can be made from gases, liquids, or solids
• Lasers produce coherent light – waves of some wavelength are aligned, and travel same direction– Incoherent light – waves of
multiple wavelengths are not aligned, travel in many directions
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Using Light
Chapter 13 Section 4
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Holography• Process used to create a three-dimensional
photographic image of an object– Illuminating objects with laser light produces holograms.– Holographic images are difficult to copy.
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Optical Fibers
• Use a process called Total Internal Reflection in order to transfer information coded in light beams.– Total internal reflection – light strikes a surface
between two materials and is completely reflected back to the first material.
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Total internal reflection