People use light and sound to send messages over a distance. A whistle tells players to stop. A doorbell tells you someone is at the door. A fire alarm warns everyone to leave. A lighthouse flashes light to warn ships about rocks, and traffic lights tell drivers when to stop and go.
You can make your own signal device. A torch can flash a pattern: one flash could mean 'yes' and two flashes 'no'. Two paper cups joined by a tight string carry your voice. A drum or a bell can be heard across a field. Loud sounds and bright lights work best for warnings, because people notice them quickly.
Worked example
Why do fire engines have flashing lights and sirens?
- The lights can be seen from far away.
- The siren can be heard even round corners.
Answer:Together they warn people to move out of the way.
Key words
- signal
- a sound or light that sends a message
- warning
- a signal that tells people of danger
- pattern
- a set of flashes or sounds that repeats
- device
- a thing made to do a job
Practise this
New questions every time.
NGSS-referenced: 1-PS4-4