The Law of Reflection
The Law of Reflection
In the lesson, you will learn about the Law of Reflection and how images are formed by plane mirrors. Click each number to learn about the Law of Reflection. Click the player to begin.
View a printable version of the interactivity.
Click on the link to launch the Who Can See Who? interactivity. You will be challenged to determine which people can see others based on their position in front of a plane mirror. You will receive immediate feedback in this interaction. This activity will assess your knowledge of the law of reflection and addresses the common misconception that a person can see anyone regardless of their position in front of a plane mirror.
This interactivity is used with permission from The Physics Classroom.
When light rays spread apart, or diverge, a virtual image is formed. If an arrow is placed in front of a mirror, an image of arrow appears at a point that seems to be located behind the mirror. This virtual image appears to emanate from the spot from which the light rays appears to be coming. The two dashed lines show where this spot is located. Of course, the light does not emanate from behind the mirror; however, our eyes see the virtual image of the tip of the arrow at the point where the two dashed lines meet. In your observations of the physlet, you should have noticed that the images formed by the plane mirror are always virtual, the same size as the object and right side up or upright.
Images formed by plane mirrors are always:
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Virtual
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Upright
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The same size as the object
Here is a brain teaser for you based on this topic. If you are six feet tall and you want to see your entire body in the mirror, how small can the mirror be?
The minimum size of the mirror is about three feet, or half of the your height. Why is this so? Think about the Law of Reflection. A light ray must be able to travel from your feet, strike the mirror, and then travel to your eye. This can only occur if the bottom of the mirror is halfway between your feet and your eyes. The light ray that travels from your head to the mirror bounces straight back, so the top of the mirror must reach the top of your head.
The Law of Reflection Practice
Now that you have explored the Law of Reflection, check your knowledge in this interactivity. Click the player to get started.