Section 1 Properties of Light - 8th Grade Physical Science

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Section 1 Properties of Light

A. Light is a wave that carries energy; a light source emits a countless number of _________________________ that travel in all directions. 1. The material through which a wave travels is called a _________________. 2. Light is an _________________________ wave that does not need a medium in which to travel.

B. For the eyes to see an object, light must strike the object and bounce off, a process called ____________________. 1. Materials that let no light pass through them are __________________. 2. ________________________ materials let almost all light pass through them. 3. Materials that let some, but not all, light pass through are __________________.

C. White light is composed of different _________________________, which have colors ranging from red to violet. 1. Objects appear to have color because they absorb some light waves and reflect others; an object appears the color of the light it ____________________. 2. All visible colors can be made by mixing light from the three primary colors of red, blue, and ____________. 3. Mixing pigment to form colors is different than mixing light to form colors; the primary pigment colors are yellow, ____________________, and cyan.

Section 2 Reflection and Mirrors

A. The law of ___________________ says that the angle of incidence is equal to the angle of reflection. 1. The uneven reflection of light waves from a rough surface is called _____________ reflection. 2. ________________ reflection results from a smooth surface such as a mirror. 3. _________________--light waves traveling in one direction are made to travel in many different directions.

Light, Mirrors, and Lenses 35

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4. Plane mirror--reflects an actual size image that seems to be behind the mirror due to the way the _______________ interprets light

B. Concave mirrors cause light rays to __________________; convex mirrors cause light rays to _________________. 1. In a concave mirror, light waves parallel to the optical axis reflect and pass through the _______________________. a. focal length--distance along the optical axis from the center of the mirror to the __________________ b. The image formed by a concave mirror depends on the ______________ of an object relative to the focal point. c. Flashlights and headlights form a _______________ of light when a light source is placed at the mirror's focal point. 2. The image formed by a convex mirror is ________________ and ________________ than the actual object; convex mirrors are used for security in stores and on vehicle outside rearview mirrors.

Section 3 Refraction and Lenses

A. Refraction 1. The speed of light a. The speed of light in ___________________ is about 300,000,000 m/s. b. Light travels _________________ when it travels through material such as air, water, or glass. 2. The bending of light waves caused by a change in speed as they pass through different media is called _____________________.

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36 Light, Mirrors, and Lenses

Copyright ? Glencoe/McGraw-Hill, a division of the McGraw-Hill Companies, Inc.

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B. _______________--transparent object with at least one curved side that causes light to bend 1. ________________ lens--thicker in the center than at the edges; forms an image based on how far the object is from the focal point 2. A _________________ lens--thicker at the edges than at the middle; causes light rays to diverge forming an upright image smaller than the actual object

C. Total internal reflection occurs when _____________ the light waves that strike the boundary between two transparent materials can be reflected. 1. At the _________________________ all the light is reflected. 2. The _________ of the critical angle depends on the two materials involved.

D. Optical fibers 1. Can make a ___________________ travel in a path that is curved or twisted 2. All the light that enters one end of the fiber comes out the other end because of ____________________________________________. 3. A thin fiber of glass or plastic, covered with another material called ______________ 4. Used in ________________________________

Section 4 Using Mirrors and Lenses

A. Compound _____________________--uses two convex lenses, the objective lens and the eyepiece lens, to magnify an image

B. A key difference between a telescope and a microscope is the ___________ of the objective lens; a telescope uses a large lens to gather light from distant objects. 1. ____________________ telescope--uses two convex lenses, an objective lens and an eyepiece, to form an image of a distant object 2. __________________ telescopes use a _________________ mirror to focus light onto a secondary mirror that directs the image to the eyepiece.

Light, Mirrors, and Lenses 37

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C. A _________________ uses a convex lens to form an inverted image on light-sensitive film. D. Unlike ordinary light, a ____________________ beam doesn't spread out as it travels.

1. A beam of light produced by an ordinary flashlight spreads out as it travels. 2. In a beam of laser light, the crests and troughs of the light waves ______________ so the

waves are in phase. a. Large amounts of energy can be applied to a very ______________ area. b. Can replace __________________ in surgery.

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38 Light, Mirrors, and Lenses

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