Transparent, translucent and opaque

What happens when something is put in the path of light? Activity 11.3 uses a torch and objects made of different materials: glass, tracing paper, cardboard, paper and thick cloth.

In a dark room, shine the torch to make a spot of light on a wall or a cardboard screen.

The activity has two steps, like real science:

• First predict: if you hold each object in front of the torch, will you still see the spot? Write your guess down.
• Then test: hold the object between the torch and the screen and note what really happens.

Do this for every object, then compare what happened with what you predicted.

The results:

• Transparent materials let light pass almost completely.
• Translucent materials let light pass partly.
• Opaque materials let no light through.

You met these three words in Grade 6, when you sorted materials by how well you could see through them. Here you sort them by how much light actually reaches the screen. The two ways agree.