Mirrors and Fibers
A mirror bounces, reflects, Light. Three instances present that idea simply: a flat mirror, a parabolic mirror and an internally reflecting fiber or pipe. A Beam of light, rather than diffuse light shows the effect of reflection and so the light source of choice is a cat toy laser; inexpensive, widely available and extremely low power.
The first step is to make the child aware of the beam since, in air, it is invisible unless something is added to scatter the beam, like a mist of water. The use of a misting spray might already be an experience in a prepared environment in connection with the care of plants.
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Misting a laser is actually an advanced exercise requiring not only two handed dexterity but a prior awareness of the beam. Not to mention a dim area, like a box or a cabinet, into which to aim the beam. Initially the child will invariably spray the source itself which she can see rather than the beam which she cannot see.
The solution is to provide a glass of opaque water. The water can be clouded with a few drops of milk. Saturating the solution with salt and giving it a stir produces a nice grainy effect. Prepared water can be a given but can also be treated as a practical life exercise. The preparation of a solution having different physical properties than the water itself is a step toward working with Chemical Reaction.
The solution is to provide a glass of opaque water. The water can be clouded with a few drops of milk. Saturating the solution with salt and giving it a stir produces a nice grainy effect. Prepared water can be a given but can also be treated as a practical life exercise. The preparation of a solution having different physical properties than the water itself is a step toward working with Chemical Reaction.
Once the child is comfortable aiming the laser the next step is to combine it with a flat, hand held mirror. Demonstrate that if the laser is aimed downward into the mirror it will appear up on the ceiling. Children really like this. Once that realization is established the mirror can be used to send the beam anywhere. Importantly the dexterity developed with this is hand-eye coordination involving both hands while looking at the actual target of the bean rather than the mirror in the hands.
Putting the mirror on the floor and bouncing the beam toward a wall provides the opportunity to vary the angle of incidence. Bouncing the beam into a second mirror instead of a wall heightens the awareness of reflection by giving it multiple stages. And even a single mirror can send a beam of light around a corner. As the mirrors become smaller and numerous the complexity of any given arrangement is unlimited.
A key development of bouncing a laser off a mirror on the floor and to a wall is the addition of a ping-pong ball. The reflecting of the beam can be seen as the same as the bouncing of the ball. This concrete experience will later be the basis of the fundamental assertion that Light behaves like both a particle and a wave.
Putting the mirror on the floor and bouncing the beam toward a wall provides the opportunity to vary the angle of incidence. Bouncing the beam into a second mirror instead of a wall heightens the awareness of reflection by giving it multiple stages. And even a single mirror can send a beam of light around a corner. As the mirrors become smaller and numerous the complexity of any given arrangement is unlimited.
A key development of bouncing a laser off a mirror on the floor and to a wall is the addition of a ping-pong ball. The reflecting of the beam can be seen as the same as the bouncing of the ball. This concrete experience will later be the basis of the fundamental assertion that Light behaves like both a particle and a wave.
Parabolic mirrors show that a curved surface creates a different effect from a flat surface and presents the idea of a focal point. The focal point being where the image inverts and where light shined into the mirror is focused.
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Fibers are used to show internal reflection and enable the understanding that Light can be guided.
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