The pinhole camera is a very simple device. It consists of a cylinder with a radius of approximately 4 cm and a height of 12 cm. There is a small hole 1 mm in diameterpositionedhalfway up the wall of the cylinder. A sheet of photographic paper 18 cm in width curves round the inside of the cylinder leaving a gap of about 1 cm just behind the pinhole. The camera is very simple to use, but it takes a long time to produce a picture. If you fix the camera outside and expose it to the light, after a few minutes, you will find that an image has appeared on the photographic paper.
CD1 Track 07
1 – You may need to adjust the volume of the microphone so that we can hear you at the back ofthe room.
Lisa: OK, as I understand it, we’ve got to build a device that will allow us to convey a ping-pong ball from one table to another a metre away. Bill what have we got?
Bill: We’re only allowed to use: six sheets of paper, a box of paper clips, some thread, four drinking straws, and two elastic bands.
Lisa: I’m not sure where to start. Anybody got any ideas?
Omar: Maybe we could use the elastic bands to launch the ball across the gap…
Bill: That’s not a bad idea, Omar, but I think that would be rather difficult to do. Hmmm…. I think we should create a sort of bridge with the sheets of paper. We could suspend it between the tables.
Omar: How would that work?
Bill: We could cut the paper into strips of about 10 cm wide…
Lisa: I get it!…and attach them end-to-end with paper clips. But how would web secure the bridge to the table?
Omar: We could use thread for that – I’m sure we could work something out. But what I’m not sure about is how we can keep the ball from falling off the bridge.
Lisa: Well, if we fold the sides of the paper so that it forms a cylinder or tube that would keep the ball from rolling onto the floor. This would also help keep the bridge rigid enough to span the distance between the tables. What do you think Bill?
