Wednesday, 20 January 2016

Traffic Lights

We had a look at something just outside our school that was designed and made by engineers.
Can you guess what it is?
It is a set of traffic lights.
 We are investigating engineering in our local area:
 We discovered some things:

  • when the green light shines for cars, then the pedestrian light shines red
  • when the red light shines for cars, then the pedestrian light shines green
  • the lights turn from green for cars, to orange, then to red.  After red they flash orange (and the pedestrian lights flash green!  This means that cars can drive IF there are no pedestrians, but the pedestrians get the right of way first.  After flashing orange the cars get a green light once more.
  • We know we can only cross the road if the pedestrian light is green, and must wait on the path if the pedestrian light is red.
We are going to design and make some model traffic lights of our own for art this week!
Back in the classroom we chatted about different colours.
First of all we had a look at the primary colours of paint: red, yellow and green.
We tried mixing these and got orange paint when we mixed red and yellow, purple when we mixed blue and red and green when we mixed yellow and blue.  We got the colour brown when we mixed yellow red and blue.
We talked about not being able to make black or white from the primary colours (or grey or pink.)
There are different primary colours for light.
Here they are:
We tried combining colours to get other colours:
Now, for our traffic lights filters we had a look at different kinds of materials:
Opaque materials won't let any light through so they won't be any use at all.
Transparent materials will let all light through but won't be coloured so they are no good either.
What we need are translucent materials that will let some light through but will allow us to have colours on our light filters.
Crepe paper is translucent,
Ordinary paper is opaque but acetates are translucent.
Tissue paper is translucent but felt is not.
Maybe we will use these when we design and make our traffic lights tomorrow.
We will also need a light source. 
We will be talking about natural and man made light sources tomorrow too.
Our materials are sorted into opaque (felt and craft paper) and translucent materials (tissue paper, crepe paper, acetates)
We made some stained glass traffic lights using the acetates,
and toilet roll traffic lights using crepe paper or acetates.
Our traffic lights on the window use a natural light source (the sun) to light up.
At PE we enjoyed a game of traffic lights where "green light" means "go", "orange light" means "prepare to stop" and "red light" means "stop".
We wrote all about our traffic lights:
Look at the lovely accounts we made of our investigation into traffic lights.
We found this colour sheet with our magnetix.
It shows examples of primary colours and translucent colours.

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