Activity 11.1.1. Warm-up Activity.
Start by writing a few sentences about your personal experience with how light travels in the real world.
Section 11.1 Ray Model for Light
Light is a critical aspect of everyday life, and its behavior in different circumstances is important to model and understand. For most everyday contexts, you can assume that light travels in straight lines, which is known as the Ray Model of Light.
Video Lesson 11.1.1. Ray Model.
Subsubsection Key Ideas
Assumption 11.1.2. The Ray Model for Light.
In the Ray Model, light is treated as a collection of rays emerging from a point source of light. Each ray may be represented as a line marked with an arrow indicating the direction the ray is traveling. You will learn in future sections when the ray model is no longer a good assumption for the behavior of light.
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a point source is any small source of light, such as a light bulb or a candle; larger sources of light, such as the sun, may be thought of as a collection of point sources
An important tool for using the ray model is to help draw Ray Diagrams, which allow you to characterize where and how light is moving through space.
Representation 11.1.3. Ray Diagram.
A ray diagram represents light as a collection of rays: straight lines that show light as traveling in straight lines marked with arrows to indicate the direction of travel, as in the figure below.
Since ray optics is concerned with light, it can help you answer questions about vision. The most basic such question is: can you see something? In general, if you want to see an object, light from that object has to reach your eye (you also need to be looking in the direction that the light comes from).
Example 11.1.5. Pinhole Camera.
A pinhole camera, also called a camera obscura, is an optical phenomenon that occurs when light travels through a very small aperture. Using the figure above, where should you stand in order to see what is on the screen? What do you see on the screen? Find other examples of pinhole cameras online. What sort of observations can you make? Can you make a pinhole camera yourself?
