Rainbows and twinkling galaxies of stars are magical occurrences for both children and adults. You probably remember your child as an infant discovering himself in a mirror for the first time. All of these objects use optics --the science of light. Children enjoy exploring how light reflects and refracts on and in varying surfaces and elements.
Before you begin activities for reflection and refraction, explain to your child that light rays travel to the earth from the sun in straight paths. Sunlight travels so fast that it takes only 8 minutes to travel from the sun to the Earth --almost 93 million miles! Optical Research Associates notes that if you could drive a car to the sun at 60 miles per hour, it would still take you 177 years to get there. In only 1 second a ray of light can go around the earth 7 times. Reflection happens when light rays hit an object and bounce back at a different angle. Refraction happens when light rays bend as they pass through an element.
After a rainy day take your child out for a walk and some puddle jumping. This is also your chance to show him that reflecting surfaces are not only mirrors. Stand by a puddle that has still water and point out that he can see his image clearly. Then stir up the water to show him how his image changes. Find other reflecting surfaces around the house such as metal pots and appliances and ask your child if he can see himself. Explain that some smooth surfaces can reflect light back making them mirrors.
Water can reflect and refract. Water bends light rays so that when you look into an aquarium, you are not seeing objects exactly where they are. Use a glass aquarium or a large glass bowl, and drop a few small objects into it. Have your child use tape to mark where the object is on the outside of the bowl. Then place a ruler into the water to show him where the object actually is. Point out that light rays going into water are refracted or bent, making objects appear to be a few inches away from where they really are.
Your child likely enjoys looking up at the night sky to see the stars. Explain to him that stars are far away and appear to be twinkling because their light is bent as it travels to the earth. The earths atmosphere causes refraction making the straight light rays from stars change angles before it reaches his eyes. Show your child why stars twinkle by shining a flashlight through a window that is clear and then through a windowpane with frosted or beveled glass. Have your child stand on the other side of the windows as you shine the beam towards him, being careful not to get the light directly in his eyes. The light through the clear window should be a straight line, but the light through the other window will scatter, making it twinkle. You can also use a candle for this easy activity.
Make A Rainbow
The next time you see a rainbow, explain to your child that a rainbow is sunlight that is being refracted by drops of water in the atmosphere or sky. This means that as light rays enter raindrops they are bent. Sunlight that looks white or invisible is actually made up of a full spectrum of colors. When it enters the water, it separates into blue, violet, green, yellow and red light. Kids can make their own rainbows by passing sunlight through a clear bowl of water. Take a clear bowl of water to a sunny windowsill and hold the bowl so that sunlight passes through the water. Kids can lay a white sheet of paper behind or below the bowl and watch as a rainbow forms on it. Let the kids experiment by holding the bowl at different angles to see if they can make the rainbow colors appear larger or brighter.