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Light Reflection

Look at the electrician on the right. He is trying to repair a fuse box in a building. The lights went out in the building, and it is very hard to see. He is using a flashlight to inspect the fuse box and find the problem. Why do you think the blue part of the fuse box is easier for him to see? The light from the flashlight is bouncing off that part of the fuse box back to his eyes. When light reflects off an object, the light bounces back to our eyes and allows us to see!

An object is seen when light is reflected from the object’s surface and enters your eyes. The human eye takes light waves and sends wave messages to the brain to be processed. The brain processes the waves as sight. Remember, the order is as follows: LIGHT OBJECT EYES

Look around your classroom. Can you see the clock? Do you recognize your friends’ faces? What color shirt did you wear today? Can you read the paper or book in front of you? You are able to see all of these things because the light in the room is hitting objects and reflecting, or bouncing, the light off of them and into your eyes. What if you turned off the lights? Could you still see the objects and colors well?

Reflect: to bounce off

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Light Reflection

How Do Mirrors Work? As you have learned, we see objects because light reflects off of their surfaces and enters our eyes. You can see the wall, the door, and the ceiling, but if you wanted to see a reflection of yourself, where would you look? You would look in a mirror!

A mirror has a very specific surface that allows it clearly reflect what is in front of it. The first mirrors were made from a stone called obsidian. The Greeks and Romans used highly polished copper and bronze for mirrors. Once glass became an available resource, mirrors were made from very smooth sheets of glass. Since glass is a poor reflector, the back of the glass is coated with silver, gold, or chrome. Mirrors can be very useful. If you stand directly in front of a mirror you can check your hair. What if you stand to the side, or at an angle to the mirror? Do you notice that you can see things at an angle to you? You can use a mirror to look around corners because of the mirror’s ability to reflect objects at an angle.

The Angles of Mirrors The thick line represents a mirror. When light strikes the mirror at an angle, it reflects at the same angle. Can you figure out the angle for the green light?

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Light Reflection

In this exercise, you will show what you know about reflection. In the diagram, the single line represents a mirror, shown from the side. The arrow is a ray of light. 1.  Draw the path of the light ray as it reflects off the mirror and reaches Point X. 2.  What if the flashlight were placed at Point Q? Draw where the light ray would go. 3.  What are some other ways you could investigate the reflection of light? Discuss

your ideas with a partner.

Point Q

Point X

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Light Reflection

Building a Periscope A periscope is a tool with several mirrors at opposite ends of a long tube. These mirrors allow people to see around objects. Designing and building a periscope is an excellent way to learn about the fundamental laws of reflection. Remember that the angle at which a light ray approaches a mirror is the same as the angle at which the light ray bounces off the mirror. Plans and instructional videos for building a periscope can easily be found on the internet. Use search terms such as “periscope plans.” For most designs, you will need the following items: ●  A long, square box or enough cardboard to make such a box ●  Two small pocket mirrors ●  A protractor ●  A sharp knife ●  Duct tape

The other end of this periscope is inside a submarine that is under water. Someone is using it to observe events above the water’s surface.

As you and your child position the mirrors at either end of the box, explain the significance of the angles at which the mirrors are set. (The first mirror must reflect light entering the periscope toward the mirror at the other end of the periscope. The mirror located at the other end must then reflect light toward the eyepiece of the periscope.) You can also watch videos of how a periscope is used onboard a submarine. Encourage your child to find other uses for a periscope. For example, a periscope can let someone look around a corner or above a couch.