Introductory Activity: Start by writing 2-4 things about the way that light travels that you are familiar with.
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.
Assumption8.1.1.The Ray Model for Light.
In the Ray Model, light is treated as a collection of rays emerging from a point source of light 1 . 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.
You will be using the ray model for light to draw Ray Diagrams. These diagrams help us figure out from where light is coming and to where light is traveling. They can be very helpful when trying to figure out how light is interacting with a particular mechanism. These diagrams will come in handy as we discuss lenses and mirrors in the next few sections.
ExercisesRay Diagram Activities
1.Exploration: What can you see in the mirror?
Stand in front of a flat mirror (like in a bathroom) and look at your reflection. You should be able to see in the mirror parts of your body that are below the base of the mirror. Use the ray model of light to explain how this is possible.
2.Practice: Pinhole Camera.
Figure8.1.2.A ray diagram of a pinhole camera. Light travels from the arrow to the back of the camera to create an image.
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?
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
