π§ͺ Science π‘ Light and sound
Waves
π In short
Waves are movements that carry energy from one place to another. Throw a pebble into a still pond and you'll see circles of waves spreading across the water. Some waves we can see, like sea waves, and some we can't, like sound, light and radio waves.
π€© Did you know?
- Waves carry energy, not matter.
- Some giant sea waves are more than 20 meters high.
- Sound waves can't travel through empty space, but light waves can.
- When waves meet, they can make each other stronger or weaker.
π Find out more
π They carry energy, not water
If you put a small leaf on a pond and a wave passes under it, the leaf bobs up and down in the same spot and doesn't travel with the wave. The wave carries energy, but the water stays roughly where it is.
π The rope experiment
Hold one end of a long rope while a friend holds the other, then shake your end quickly up and down, and a wave will travel along the rope to your friend's hand!
π‘ Crest and trough
Every wave has a high crest and a low trough. The distance between two crests in a row is called the wavelength, and the number of waves passing each second is called the frequency.
π― Waves we can't see
Sound is waves traveling through air, light is waves too, and so are the radio waves that carry broadcasts to radios and phones, and the X-rays doctors use to photograph bones.
𧩠Test yourself
1 What do waves carry?
2 What do we call the highest point of a wave?
3 Some giant sea waves are more than ?? meters high.
4 Which picture shows βWavesβ?
π§ͺ Discover more
π· Picture sources: Wikimedia Commons
- Roger McLassus Β· CC BY-SA 3.0
