What is light?
Light does not appear by itself; it always comes from a source. Natural sources: the Sun, stars, lightning, fireflies and some deep-sea creatures. Artificial sources: lamp, candle, fire, torch. Light travels in straight lines as rays, so a shadow forms behind an obstacle. The Moon is not a source of light: it reflects sunlight. We see an object when its surface sends light back to our eyes. A white object reflects almost all the light, a black one absorbs most of it and warms up, so on hot days we stay cooler in white or pale clothes. A transparent object (glass) lets light pass. Sunlight also contains ultraviolet rays that we cannot see, which can burn the skin.
Shadow theatre: in a dark room use a torch and your hands to make a rabbit or bird shadow on the wall. Move the torch nearer or farther and watch how the size of the shadow changes.