What do you need?
Three pieces of cardboard, candle, needle.
What do you do?
1. Make a hole through the centre of each of three pieces of the cardboard using a needle.
2. Place the three pieces of the cardboard upright and 30 cm apart from each other.
3. Place a lighted candle in front of the cardboard furthermost from where you stand.
4. Arrange the three pieces of the cardboard s0 that the candle flame can be seen through the holes.
5. The shift one the pieces of the cardboard to one side.
6. Try to observe the flame of candle again. Can you see it now?
What do you find?
1. We are able to see the candle flame through the hole when they are in a straight line.
2. When any one of them is not in the line with others, the candle flame will be blocked by the cardboard. Therefore the light is not visible to eye.
What do you conclude?
Light travels in straight lines.