Light is known to behave in a very predictable manner. If a ray ripple tank experiment refraction light could be observed approaching and reflecting off of a flat mirror, then the behavior of the light as it reflects would follow a predictable law known as the law of reflection. The diagram below illustrates the law of reflection. Reflection and the Locating of Images It is common to observe this law at work in a Physics lab such as the one described in the previous part of Lesson 1.
To view an image of a pencil in a mirror, you must sight along a line at the image location. As you sight at the image, light travels to your eye along the path shown in the diagram below. It just so happens that the light that travels along the line of sight to your eye follows the law of reflection. For example, in Diagram A above, the eye is sighting along a line at a position above the actual image location. For light from the object to reflect off the mirror and travel to the eye, the light would have to reflect in such a way that the angle of incidence is less than the angle of reflection.
In Diagram B above, the eye is sighting along a line at a position below the actual image location. Consider the diagram at the right. Which one of the angles is the angle of reflection? A ray of light is incident towards a plane mirror at an angle of 30-degrees with the mirror surface. What will be the angle of reflection? The angle of reflection is 60 degrees.
60 degrees since the angle of incidence is measured between the incident ray and the normal. Perhaps you have observed the image of the sun in the windows of distant buildings near the time that the sun is rising or setting. However, the image of the sun is not seen in the windows of distant building during midday. Use the diagram below to explain, drawing appropriate light rays on the diagram. A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of 45-degrees with the mirror surface. Trace the path of the light ray as it bounces off the mirror.
Continue tracing the ray until it finally exits from the mirror system. How many times will the ray reflect before it finally exits? The light reflects twice before it finally exits the system. 1996-2018 The Physics Classroom, All rights reserved. The wave doesn’t just stop when it reaches the end of the medium.