Laser Experiments to Share with Your Kids

Date Updated: October 25, 2024

Note: A parent should always be present when children are conducting a science experiment at home. Even the simplest experiments are potentially dangerous.

LASER is an acronym that stands for Light Amplification by Stimulated Emission of Radiation, and it’s a device that emits a concentrated beam of photons, the basic units of electromagnetic radiation—another word for light.

A laser controls the way energized atoms release photons, focusing the light energy into a narrow beam; meanwhile, mirrors are used within the laser device to make the photons bounce off each other and charge up. Light particles from a regular or incandescent bulb are not concentrated, and they scatter out in all directions. Although light energy will behave in the same way whether it comes from a light bulb or a laser, the concentration of light in the beam of the laser will allow you to see how light waves work.

One of the principles you will observe while looking at a laser is the Law of Reflection, which states that when an object bounces off a flat surface, the angle at which it hits a flat surface will be equal to the angle at which it bounces away. This angle changes when the surface is not perfectly flat.

When a light wave reaches a boundary, like the wall of a container or a piece of glass, it will bend. This is called refraction. When a beam exits on the other side of the boundary (we call this the pass-through beam), the angle will be different depending on the characteristics of the boundary, such as its thickness, smoothness, and transparency.

Before we start experimenting with lasers, you'll need eye protection to shade your eyes, such as large-frame sunglasses or tinted UV ski goggles. Even with that protection, though, it’s important that you avoid shining a laser beam into your eyes or those of others, since this can be dangerous. Another note: For these experiments, it’s best to use keychain-type lasers from a toy or discount store. The green lasers sold in astronomy stores are too dangerous for uncovered eyes.

Here are a few experiments you can try. Once you’ve set up the experiment, darken the room as much as possible for the best effect.

Plastic Bottle Beam. Fill a clean plastic water or soda bottle with water and add a sprinkle of cornstarch. Turn down the lights and turn on your laser, aiming the beam through the bottle. Do you see the beam in the bottle? Can you find the reflection beam and the pass-through beam?

Light Bulb Glow. In the dark, aim your laser at a frosted incandescent light bulb. The bulb will glow and have several internal reflections!

Reuse Old CDs. Shine your beam over the surface of an old CD or DVD. You should see between five and 13 reflections off the surface, depending on where you shine the laser, how many scratches there are on the surface, and how good the visibility is in your room.

Different Glassware Types. Pass the laser beam through objects such as wine glasses or clear glass vases. How does the beam pass through differently between plastic and glass, or between smooth and multifaceted surfaces? Can you find the pass-through beam as well as a reflected beam?

Characteristics of Lenses. If you have an old pair of eyeglasses, pop out the lenses. Direct the beam through one lens. Try it at several places on the lens and see how light passes differently through parts that are thicker, thinner, and angled. Take the second lens and line it up a few inches away from the first to see how the light wave bends when it moves through both lenses.