Light
We all need light in order to see things. We get light from different light sources, the sun, the stars, flames and light bulbs. If we didn't have any light it would be quite dark.
For us to see the things around us, the light from a light source bounces off these objects and into our eyes. Our desk, cup or pen doesn't give off its own light, it just reflects light into our eyes.
Some objects are more reflective than others. Shiny objects, like a mirror, reflect all of the light that shines on them. Other objects which are dark, such as a table, absorb most of the light that shines on them.
WARNING!
The sun gives off very strong light and you must NEVER look directly at the sun. Sunglasses protect your eyes from the sun but you can still damage your eyes if you look at the sun through sunglasses. What could happen? You can go blind, and that's not just something your parents say, it's a fact.
Shadows
Light travels in straight lines which means it cannot bend. So when something gets in the way it forms a shadow, an area of dark where no light can get to.
Shadows change depending on how close the light source is to the object. If the object is close to the light source you will get a big shadow. If the object is far away from the light source you will get a small shadow.
Shadows - Find a torch or a lamp and put your hand in front of it to make a shadow. See what happens to the size of the shadow when you move your hand forward and back from the light source. What do you notice?
Sounds
We hear sound when something vibrates. The vibrations make the air next to it vibrate and these airwaves travel to our ear to vibrate our eardrum. Vibrations can travel through materials like walls, glass and water. Have you ever been swimming and gone underwater? What does it sound like? It sounds different, doesn't it? This is because the vibrations get distorted by the water and it is not so clear when it gets to our ear.
What changes the sound?
Loud noises create more vibrations whereas quiet noises create smaller vibrations.
Sounds that are far away are quieter because the longer the vibration has to travel the more it will die out. Sounds that are near to us sound louder as we hear them when the vibration is at the strongest.
Videos on how sound works
Pitch of a sound
A pitch is how high or low the note is. A pitch is changed by making the string that you are vibrating shorter or longer. A short or small vibrating string will give you a high pitch. A long or large vibrating sting will give you a low pitch.
Make your own instrument - All you need is a box and different sized elastic bands. Tie the elastic bands around the box. Try plucking the bands. How do they sound? Did you notice that the small elastic bands have a different pitch to the large ones?
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