Lighten up!

Transcription

1 Lighten up! Light is all around us, illuminating our world. It is colourful, bendy, bouncy, and can pack some pretty intense energy. Explore the funny ways light travels through air, water, and even jiggly gelatine with these experiments. Enlighten your mind with these fun activities to discover what light is, and what colour has to do with it.

2 Light and Dark The colour of your clothing can change more than just your style, it can change your temperature too. What You ll Need two ice cubes (each about the same size) 1 page of black construction paper 1 page of white construction paper a stopwatch or clock a sunny day 1. Find a sunny spot outside. 2. Place both pieces of construction paper on a flat surface. 3. Put an ice cube on each piece of paper. 4. Watch the ice cubes and time them to see which one melts first. Light coloured surfaces reflect light, so they stay cool in sunlight. Dark coloured surfaces absorb light, so they become hotter in sunlight. This is why the ice cube on the black paper melted first. If you want to stay cool on a hot day, which coloured clothing should you wear?

3 Light travels in a straight line, but when it enters a new material, it bends and changes direction. When light bends, we call this refraction. Use water to bend light in these next two tricks to wow your friends. Broken Pencil Materials clear drinking glass pencil water 1. Fill the drinking glass ⅔ full with water. 2. Place a pencil in the glass on a slant (like in the picture). 3. Look at the glass straight on to see the broken pencil. The light rays that are reflected off the upper half of the pencil travel straight (through air) to your eyes and appear normal. The light rays reflecting off the bottom of the pencil (through water, then air) are bent because of refraction. This makes the pencil appear broken in the middle, where the air and water meet.

4 The Disappearing Coin Materials a coin a plastic bowl (not transparent) clear tape water 1. Use a small piece of tape to attach the penny to the bottom of the bowl. 2. Take a few steps back from the bowl until the penny just disappears behind the rim of the bowl (see image A above). 3. Stand still and have someone else pour water into the bowl until it is ¾ full. When the water is poured into the bowl, the penny re-appears (image B above). The water that was added bends (or refracts) the light over the lip and redirects it towards your eyes. See the before (A) and after (B) pictures above to see how the water affects the light rays. A B

5 A Rainbow of White Did you know that white light is actually made up of all the colours of the rainbow? Try the experiment below to see for yourself. Materials ½ page of cardboard (from a cereal box or other sturdy material) coloured markers, pencils or crayons (red, orange, yellow, green, blue, purple) glue stick scissors string (2 metres) pen or other object with sharp tip spinner template page (included in this activity) 1. Print off the template page from the computer. 2. Colour in each triangle of the circle different colours by matching the letter with the colour: Red, Orange, Yellow, Green, Blue, Violet 3. Glue the circle onto the cardboard. 4. Cut out the circle. 5. Use the tip of the pen to punch out the two small holes near the centre of the circle. 6. Loop the string through the two small holes, leaving about 40 cm of string on both sides of the disk. Tie the two ends of the string together to close the loop. It should look like in the photo to the right. 7. Hold both ends of the string tight and have another person wind up the string by spinning the coloured disk. You will need to wind it about 30 to 40 times. 8. Release the disk and let it spin - hold the string tight and look at the coloured side. This works best by looking at the disk straight on while it s spinning. In this experiment, the colours on the disk move so fast that you see them all blended together as a whitish colour. This is a cool way to show that the white light is actually made up of all the colours of the rainbow. We see the reverse when we look at rainbows in the sky white light from the sun gets separated by raindrops into many colours.

6 V R B O G Y Y G O B R V

7 The Gelatine Prism Experiment Use gelatine to explore how light moves through different materials and shapes. Materials 1 package of red gelatine powder such as Jell-O (not sugarless) Square 8 x 8 inch baking dish Bread knife or cookie cutters Red laser pointer 1. Make the red gelatine as described on the package into an 8 x 8 inch baking dish. Let it chill overnight or until hardened. 2. Remove the gelatine block from the dish onto a clean surface. 3. Use the bread knife or cookie cutters to cut out geometrical shapes like the ones below: Laser pointers can damage your eyes. Never point a laser close to a person s face. 4. Place the gelatine cut-out shapes on a flat surface, and shine the laser through one side. What happens to the light as it passes through? 5. Experiment with different shapes and angles of light. As the light travels from air to gelatine and back again it is bent, or refracted, and changes direction on the other side. You are able to see the laser beam inside the shapes because it is reflecting off the tiny particles of gelatine. This experiment will only work if your laser and the gelatine are the same colour, because all other laser beam colours will be absorbed by the gelatine. If you ve only got a green laser pointer, you should use green gelatine instead.

8 For the Experiments two ice cubes 1 page of black construction paper 1 page of white construction paper A clear drinking glass a pencil a coin a plastic bowl (not transparent) clear tape ½ page of cardboard coloured markers, pencils or crayons (red, orange, yellow, green, blue, purple) a glue stick scissors string (2 metres) 1 package of red gelatine powder such as Jell-O (not sugarless) a square 8 x 8 inch baking dish a bread knife or cookie cutters a red laser pointer Book The Kids' Book of Kaleidoscopes By Jack Romig and Carolyn Bennett This kids' book of kaleidoscopes turns ordinary kids into masterful kaleidoscope builders. (Workman Publishing Company, 1994) Web link Tell Me About Light! Explore more about the science of light, and find answers to commonly asked questions about light and lenses. hoolzone/info_light.cfm