How is a laser beam different than a light beam? Can I make a laser beam?

Question Answered by Brian A Pyper, PhD, Professor of Physics,
BYU-Idaho Director of Physics Education

Light comes from electrons in their shells around atoms getting excited and falling back down to lower energy levels. When they do this they emit the energy difference as light. Regular light will usually come from lots of different kinds of atoms whose electrons are at different energy levels and at different stages of excitement and at different times. This is how flashlights, light bulbs, fires, candles, glowsticks, and even luminescent algae work.

The word “laser” is an acronym for “Light Amplification by Stimulated Emission of Radiation.”

Laser light is special because all the atoms involved are of the same kind and stimulated and released at the same time. This makes it so laser light is all the same color (mono-chromatic) and all in the same phase – it’s undergoing the same part of its electro-magnetic wave motion at the same time (coherent). The result is that laser light doesn’t scatter as much as regular light – it will travel LONG distances (like to the moon!), and although it will reflect (like in a mirror) and refract (bend like in a lens) it won’t disperse (like light does in raindrops to make rainbows).

Making your own laser is fun and not too hard if you use a laser diode and a couple of watch batteries. Be careful not to shine it into eyes or at aircraft.

What is a laser? A laser is usually made up of a tube with mirrors at both ends. One mirror is partly transparent (see-through). Inside the tube is some type of material, such as gas, crystal, or liquid.

A powerful lamp or some other source of energy adds energy to the material. Then the material produces light. The light bounces back and forth between the mirrors at the ends of the tube. As it does so, it causes the material in the tube to produce more light. Some of this light escapes through the partly transparent mirror. (Credit: Britannia Kids)

Make a Laser Obstacle Course
We will use the law of reflection to design an “obstacle course” for a laser using three mirrors to direct the laser beam to a target.

The Law of Reflection

The Law of Reflection
Light can bounce or reflect. The image you see when you look in a mirror is a reflection.

The law of reflection says that, no matter which direction light hits a smooth surface from, the light reflects back off at an equal angle.

Materials: large area, laser pointer, three 3″x5″ mirrors, binder clips or clothespins, paper, box, masking tape

Set up the equipment for the laser maze.

  1. Draw a bullseye target on the paper. You can decide how large you want your target to be. Tape or glue the target to a box (a cereal box works well).
  2. Use binder clips or clothespins to make your mirrors stand up perpendicular to the floor. If they aren‘t placed straight up, your laser won’t be reflected where you want it to go.
    Now you’re ready to create the laser course.
  3. Tape your laser to the starting location of your maze. You may need a box to raise the laser up.
  4. Place the mirrors strategically using the law of reflection to reflect your laser beam to hit the target. You might want to start with one mirror and work up to all three.

Laser Course Rules:

  • The laser must be turned off while you are moving mirrors. Lasers can hurt eyes when shining directly into them.
  • The target must be placed 4 feet away from the laser and not straight in front of it.
  • Mirrors must be 1-4 feet away from each other and the laser.
  • Once the laser position is set, it cannot be moved.

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