الأسبوع 29 · المحور 4، الباب 3 «وسائل التواصل» (ب): رسائل الضوء والصوت وطريقة برايل · 3 دروس
1
Light messages
Discover P2 Term 2: Axis 4, Chapter 3
GoalSend a simple message with light, sort things by what they do to light, and show that light travels in straight lines.
New words
beam · a stream of light that goes in a lineblock · to stop light from passing throughreflect · to bounce light back in a new direction
Explanation
We can use light to send a secret message. Flash a torch on and off, and agree what the flashes mean. Light travels in straight lines. A beam from a torch goes straight until something gets in its way. Some things let light pass through, such as clear glass. Some things block light, such as a book or a wooden door, and they make a shadow behind them. Some things, such as a mirror, reflect light. They bounce it back in a new direction. We never shine a torch or a mirror into anybody’s eyes, and we never look at the Sun.
Worked examples
Flashes
Means
1 flash
I am ready
2 flashes
stop
3 flashes
come here
Jana and Karim agree on a secret light code for the classroom.
A book blocks the light, so a dark shadow forms behind it.
A grown-up holds three cards with holes in a line. The torch beam passes through all the holes. If one card is moved, the beam is blocked. Light travels in a straight line.
Class activity
Light detective. In a dim room, with a grown-up, test six things with a torch: a clear plastic cup, a book, a mirror, a spoon, a sheet of paper and your hand. Predict first. Does the thing let light through, block it, or bounce it? Make a table of your results. Never shine the torch into eyes, and never use sunlight.
Practice
1
Name one thing that lets light pass and one that blocks light.
For example: clear glass lets light pass; a book blocks it.
2
Why is there a shadow behind the teddy?
The teddy blocks the light.
3
A torch is pointed at a mirror. What does the mirror do to the light?
It reflects the light. It bounces it back.
4
Why must we never shine a torch into someone’s eyes?
