The bright rays of the sun, the twinkling of the stars, the warm glow of a candle, blinding headlights or a cutting-edge laser beam – these are all forms of light, information-laden streams of energy. Energy is made visible to the eye in light, we can feel it in heat, and we can hear it in sound.

But how is it possible for light to etch images of things on the cornea of the eye or on a projection screen? To find the answer to that, one must imagine light as a bundle of straight rays, something like a thin ray of the sun shining through a space between the leaves of the trees onto the forest floor.

If such a bundle of rays fell through a hole, it would project a picture on the opposite wall.

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