Background Information & Activities
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What do many living things need to survive? Most plants and animals rely on food, water, shelter, and light in some way. In this movie, children will learn about an energy that is all around us and helps us see the world: light! But what is light? Remind children that light is a type of energy, like heat or sound. The Sun, stars, lightning, and fire are all natural sources of light. Living things need light to survive, including plants, animals, and people. People use electricity to light their homes and some use solar power, which converts sunlight into electricity. Light is made up of tiny particles that travel in waves. Light travels until it hits an object and is either absorbed or reflected. We can see because light is reflected from an object to our eyes. Light can pass through transparent, or clear objects, but not through opaque ones. Objects that block light can cast shadows. Colored glass objects block some light but also allow some light to pass through, while translucent objects, like frosted glass or wax paper, diffuse light and prevent clear vision of whatever is on the other side.
Many living things rely on light to survive. Plants convert sunlight into food via photosynthesis to grow and change. Cold-blooded animals such as reptiles, amphibians, and insects rely on light to warm their bodies. People need light to grow crops, but they also need light to see. People use electricity to power their light bulbs and light their homes. Many buildings and electronics use solar power, a renewable energy resource which uses special devices that convert sunlight into electricity.
Remind children that light moves very, very quickly—at 186,282 miles per second, or 299,792,458 meters per second. Light rays travel in one direction until they hit an object. Light reflects, or bounces off the object and into our eyes so we can see it. The object also absorbs, or takes in, some light. Objects that are shiny, such as metal pots and mirrors, reflect light better than dull objects such as dark sweaters or fuzzy toys, which absorb more light. Smooth, flat mirrors reflect light in roughly the same angle the light hits them so we can see reflections. When light hits curvy mirrors, it bounces off in many different directions and back to our eye. We see our reflections, but they are distorted.
Light can easily pass through some objects, such as clear plastic or glass. These objects are transparent and we can see through them. Light cannot pass through opaque objects, such as wood blocks. Objects that block light can cast shadows. Show children that when an object blocks light, light cannot pass through to the other side. You see a dark spot that’s shaped like the object—a shadow. This is how we know that light travels in straight lines; if it curved, it would bend around opaque objects and shadows would not be made. Some objects block some light but also allow some light to pass through. Sunglasses and stained glass block some light. Translucent objects diffuse light in many different directions. It is difficult to see through translucent objects such as sheer fabric, wax paper, frosted glass, or tissue paper.
When light passes through objects, it refracts, or changes direction. Place a spoon in a clear glass of water. What happens? The spoon looks like it’s broken. When light travels through water or glass, it slows down and changes directions or “bends.” Then as it passes through to air, it speeds up again. This changes the way we see the object. Binoculars, telescopes, microscopes, and magnifying glasses all refract light in different ways so we can see things in closer detail.
Light is a complex and fascinating subject that children can explore all on their own.
A swimming pool at 30°C is at a lower temperature than a cup of tea at 80°C. But the swimming pool contains more water, so it stores more thermal energy than the cup of tea.
