Ch. 18 Notes 3/28/16

Transcription

1 Section 1 Light & Color: Vocabulary Transparent material: transmits most of the light that strikes it. Light passes through without being scattered, so you can see clearly 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. Frosted glass, wax paper. Opaque materials: reflects or absorbs all light that strikes it. You cannot see through opaque materials because light cannot pass through them. Primary colors: three colors that combine to make any other color. Secondary colors: two primary colors combined in equal amounts. Complementary colors: any two colors that colors that combine to make white (primary + complementary) Pigment: colored substances used to color other materials Transparent transmits most of the light that strikes it can see clearly what's on the other side Translucent scatters light as it passes through can see something behind it, but details are blurred Opaque 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 primary colors (yellow, cyan, and magenta) Complementary: primary and secondary color combine to form white 1

2 Pigments colored substances used to color other materials. When Light Strikes an Object 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 Why is an apple red? What color does a green leaf appear to be in red light? Why? What are the primary colors of light? What happens when you combine the three primary colors of light in equal amounts? If you look at an apple through a blue filter what color will it appear? Why? What are the secondary colors of light? How are they made (what colors make them)? 2

3 Pigments Section 2: Reflections and Mirrors As pigments are added together fewer colors of light are reflected and more are absorbed. Primary: What happens when you combine the primary colors of pigments? What are the secondary colors of pigments and how are the made? The more pigments you combine the the mixture looks. Ray: a straight line with an arrow, used to represent a light wave Regular Reflection: occurs when parallel rays of light hit a smooth surface. All light rays are reflected at the same angle because of the smooth surface, you see a sharp, clear reflection. Diffuse Reflection: when parallel rays of light hit a bumpy surface or uneven surface. Each light ray hits the surface at a different angle because the surface is uneven. So, the reflection you see isn t clear. Plane mirror: flat sheet of glass that has a smooth, silver colored coating on one side. Image: copy of an object formed by reflected or refracted light. Virtual image: an upright image that forms where light seems to come from. The image appears to be behind the mirror, but you can 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 surface that curves inward like the inside of a bowl. Optical axis: imaginary line that divides a mirror in half. Similar to the equator on Earth. Focal point: point at which rays parallel to the optical axis meet. Convex mirror: mirror with a surface that curves outward. 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 Plane mirrors The image is always upright, virtual, and the same size as object. *Virtual means the image forms where the light appears to come from. The image appears to be behind the mirror. Concave mirrors Convex mirrors Concave mirror where object is beyond focal point Produces real, reduced, inverted image. 3

4 Concave when object is beyond focal but near it Produces an image that is real, inverted, and enlarged Concave mirror where object is closer than focal point 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 Lenses 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. Refraction of light How does density relate to the index of refraction? The higher the index of refraction of a medium the it bends light The lower the index of refraction of a medium the light waves travel through it. A prism forms a rainbow because the different colors of light have different wavelengths. This causes the colors to be refracted at different amounts. This causes white light to separate into a rainbow. Index of Refraction Rank the following medium according to how fast light travels through them. Water Glass Air Glass causes light to bend more than air does. Which material has a higher index of refraction? 4

5 Mirage Lenses Convex Lens Convex Lens 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 Always form a virtual image because the parallel rays of light that pass through the lens never meet. Difference between mirrors and lenses 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 5