Ch. 1 8 Notes
3/28/16
Section 1 L ight & Color: Vocabulary
Transparent
• Transparent material: transmits most of the light that strikes it. Light passes through without being scattered, so y ou can see c learly what is on the other side. Ex. Clear glass, water, and air • Translucent materials: scatters light as it passes through. Can usually see something behind a translucent object, but details are blurred. Ex. F rosted glass, wax paper. • Opaque materials: reflects or absorbs all light that strikes it. You c annot see through opaque materials because light cannot pass through them. • Primary colors: three colors that c ombine to make any other c olor. • Secondary c olors: two primary colors combined in equal amounts. • Complementary colors: any two c olors that c olors that combine to make white (primary + complementary) • Pigment: colored substances used to c olor other materials
• transmits most of the light that strikes it • can see clearly what's on the other side
Translucent
Opaque
• scatters light as it passes through • can see something behind it, but d etails are blurred
• reflects or absorbs all light that strikes it • Can't see through, no light passes through
Colors • Primary colors of light are: they combine to make every other color • Secondary: produced by combing two p rimary
colors (yellow, cyan, and magenta) • Complementary: primary and secondary color
combine to form white
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Ch. 1 8 Notes
3/28/16
Pigments
When L ight Strikes an Object
• colored substances used to color other materials.
• Three things can happen:
• Color depends of two things:
Opaque objects
Transparent and Translucent objects
Why is a banana yellow?
• Why do we see certain colors with transparent and translucent objects?
• Ex. Filters Red filter only lets red wavelengths through
Colors of Light • What are the primary colors of light? • Why is an apple red?
• What color does a green leaf appear to be in red light? Why?
• If you look at an apple through a blue filter what color will it appear? Why?
• What happens when you combine the three primary colors of light in equal amounts?
• What are the secondary colors of light? How are they made (what colors make them)?
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Ch. 1 8 Notes
3/28/16
Pigments
Section 2 : Reflections and Mirrors
• As pigments are added together fewer colors of light are reflected and more are absorbed.
• Ray: a s traight line with an arrow, us ed to repres ent a light wave • Regular Reflection: occurs when parallel rays of light hit a s mooth s urface. All light rays are reflected at the s ame angle becaus e of the s mooth s urface, you s ee a s harp, clear reflection. • D iffus e Reflection: w hen parallel rays of light hit a bumpy s urface or uneven s urface. Each light ray hits the s urface at a different angle becaus e the s urface is uneven. S o, the reflection you s ee is n’t clear.
• Primary:
• Plane mirror:
flat s heet of glas s that has a s mooth, s ilver c olored coating on one s ide.
• Image: copy of an object formed by reflected or refracted light.
• What happens when you combine the primary colors of pigments? • What are the secondary colors of pigments and how are the made?
• Virtual image: an upright image that forms where light s eems to come from. The image appears to be behind the mirror, but you c an’t reach behind the mirror to touch it. • Real image: forms when rays actually meet. They are larger ups ide down and can be larger or s maller than the object. • Concave mirror:
mirror s urface that curves inward like the ins ide of a bowl.
• Optical axis : imaginary line that divides a mirror in half. S imilar to the equator on Earth.
• The more pigments you combine the ______ the mixture looks.
Types of reflections • Regular: A clear image is produced because the rays hit a smooth surface • Diffuse: Creates a blurred image because the rays hit a bumpy surface
Concave mirrors Convex mirrors
• Focal point: point at which rays parallel to the optical axis meet. • Convex mirror:
mirror with a s urface that curves outward.
Plane mirrors The image is always upright, virtual, and the s ame s iz e as object. *Virtual means the image forms where the light appears to come from. The image appears to be behind the mirror.
Concave mirror where object is beyond focal point Produces real, reduced, inverted image.
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Ch. 1 8 Notes
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Concave when object is beyond focal but near it
Concave mirror where object is closer than focal point
Produces an image that is real, inverted, and enlarged
A virtual, upright, enlarged image forms
Convex mirrors always form virtual, upright, and smaller images, because the rays never actually meet.
Section 3 : Refraction and L enses
Refraction of light
Index of Refraction
• Refraction: when light rays enter a medium at an angle, the change in speed causes the rays to bend, or change direction. • Index of Refraction: measure of how much a ray of light bends when it enters that material • Mirage: image of a distant object caused by refraction of light. • Lens: curved piece of glass or other transparent material that is used to refract light. • Convex lens: thicker in the center than at the edges. • Convex lens: thinner in the center than at the edges.
• How does density relate to the index of refraction?
• Rank the following medium according to how fast light travels through them.
• The higher the index of refraction of a medium the _______ it bends light • The lower the index of refraction of a m edium the _______ light waves travel through it. • A prism forms a rainbow because the different c olors of light have different wavelengths. This causes the colors to be refracted at different amounts. This causes white light to separate into a rainbow.
• Glass causes light to bend more than air does. Which material has a higher index of refraction?
• Water ________
Glass ________
Air________
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Ch. 1 8 Notes
3/28/16
Mirage
Lenses
Convex L ens
Convex L ens
Real image is produced if object is further from lens than focal point.
Virtual image is produced if object is closer to lens than focal point.
Concave lens
Difference between mirrors and lenses Always form a virtual image because the parallel rays of light that pass through the lens never meet.
• Mirrors have a coated on the back and lenses do not • This lets light rays go through lenses to produce real images and with mirrors real images re produced on the same side as the mirror
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