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chapter 30 physic
| Question | Answer |
|---|---|
| What is refraction? | a change in direction where a light ray bends as it enters glass and bends again as it leaves |
| How is refraction caused? | changing the speed of light traveling in different media (of different refractive index) |
| How does a lens form an image? | by bending parallel rays of light that pass through it |
| what is a lens? | a piece of transparent material, such as glass or plastic, that can bend parallel rays of light so that it forms images |
| What is the shape of a convex lens? | thick in the middle and thin around the edges |
| What does a convex lens do? | causes rays of light to converge or come to a focus. |
| What lens is thick around the edges and thin in the middle? | concave |
| what does a concave lens do? | causes rays of light to diverge or spread apart |
| Where does light appear to come from? | a single point |
| What happens with rays of light that pass through the center of either a converging or a diverging lens? | passes straight through without bending |
| when do rays of light bend more? | if they pass through the lens nearer the edges |
| What is the center of curvature? | curved surface of a lens is made as a portion of a spherical surface. the center of the sphere is called the center of curvature of the surface. every point on the surface is equidistant to it. |
| what is the line joining the centers of curvature on either side of the lens? | principal axis |
| what is focal point? | the point at which rays of parallel light converge or seen to converge. |
| When does a lens have two focal points? | light can go through a lens from either side one on either side of the lens |
| What is the plane passing through either a focal point of a lens that is perpendicular to the principal axis? | focal plane |
| what is focal length? | distance between the center of the lens and its focal point |
| what does the type of image formed by a lens depend on? | the shape of the lens and the position of the object |
| what is an image? | a likeness of an object |
| There are two types of images that can be produced by converging (convex) lenses. what are they? | virtual and real |
| What is a virtual image? | an image that can be seen by an observer but cannot be projected onto a screen |
| What do the light rays not do? | they do not come to a focus |
| When is the image formed? | when the object is between the lens and the focal point |
| What is a real image? | an image that can be projected onto a screen because the light rays do come to a focus |
| What is the orientation of a real image | upside down |
| when is a real image formed? | when the object is outside the focal point |
| Give some uses for converging lenses that form a real image? | projecting slides, transparencies or movies on a screen. |
| What are images formed by diverging lenses like? | image is ALWAYS right side up, virtual, smaller. |
| What is used to construct a ray diagram? | the size and location of the object, its distance from the center of the lens, and the focal length of the lens |
| What can a ray diagram determine? | the size and location of an image |
| When does a ray parallel to the axis pass through the focal point? | after refracting in the lens |
| When a ray goes through the center where does it continue? | in a straight line |
| Where does a ray through the focal point move? | parallel to the axis after it refracts |
| Where is the image formed? | where these 3 sample rays intersect or appear to intersect. two of these three rays is sufficient to locate the relative size and location of the image. |
| Convex lenses: What does the position of the object in the relation to the focal point determine? | the size and type of the image |
| Where do lights of ray diverge? | after leaving the lens |
| What is the image formed by when they diverge after leaving the lens? | extending lines backward to where they appear to come from |
| A ray through the center continues.... | straight |
| Where does a ray that is heading toward the focal point bend? | parallel to the axis |
| Where do the rays diverge? | after leaving the lens |
| How is the image located? | by extending lines backwards to the point where they APPEAR to come together |
| What does a converging lens form? | either a real or a virtual image |
| When a real image is formed, WHERE is the image and object? | ALWAYS on opposite sides of the lens |
| When a virtual image is formed, WHERE is the image and object? | ALWAYS on the same side of the lens |
| Why do most cameras use compound lenses? | to minimize distortions called aberrations |
| What is a common type of telescope? | Astronomical |
| How many lenses does an astronomical lens use? | two |
| What is the eyepiece? | the lens which is closest to the eye and magnifies the real image produced by the first lens |
| What is the image like for an astronomical telescope? | inverted |
| Terrestrial telescope: How many lenses does it use? | three or a pair of reflecting prisms to produce an upright image |
| What do refracting telescopes use? | lenses |
| What do reflecting telescopes use? | mirrors |
| Where does the image form for nearsightedness? | it forms in front of the retina |
| How do you correct nearsightedness? | Diverging lenses (concave) |
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16_dnuckolls
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