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19/02/2013 Unit C: Lights & Optical Systems Topic 2: Reflection A. Introduction 1. Reflection is the process in which light strikes a surface and bounces back off that surface. How it bounces off the surface depends on the ____ ___ ____________ and the type of surface it hits. If it hits a rough surface, the light is ___________. If it hits a smooth surface, the light _______________ ____________________________ to the angle it hits. 1 19/02/2013 2. Light coming from a light source is called an __________ ______ and the light that bounces off the surface is called a __________ ______ . 3. A line that is ___________ ( 90o with the surface) to the plane mirror is called the normal line. 4. The angle between the incident ray and the normal line is called the angle of ____________ ( i ). 5. The angle between the reflected ray and the normal line is called the angle of ____________ ( r ). B. Forming An Image 1. The Law of Reflection states that: _________________________________________ • The incident ray, the normal line and the reflected ray lie in the same plane (an imaginary flat surface) C. Curved Mirrors 1. Convex mirrors a) b) Mirrors that __________ out Convex mirrors form images that appear much smaller and farther away than the the object - but they can reflect light from a large area, making them useful as security devices. 2 19/02/2013 2. Concave Mirrors a) Mirrors that _________ in b) Concave mirrors form an image that appears to be closer than it actually is and can be useful because it can also reflect light from a large area - side mirrors on automobiles. D. Using Reflections 1. Reflectors help to make _________ and _________ visible at night. 2. A reflector is made up of hundreds of tiny, flat reflecting _________ arranged at 90o angles to one another. 3. These small surfaces are packed side by side to make the _________ . 4. When light strikes the reflector the light bounces off the tiny surfaces and bounces _________ toward the light source. 5. Pool players use the law of reflection to _________ their game. 6. Like a light ray, a pool ball travels in a _________ line. In a 'bank shot' (Figure 3.25, p. 199) the cue ball is bounced off the cushion at an angle which enables the player to hit the target ball. 7. This angle is calculated as the angle of _________ (with the cushion) is equal to the angle of _________ (with the target). 3 19/02/2013 Page 199 #’s 1-4 4