Question

Draw a labelled diagram of an experiment to show rectilinear propagation light.

Answer 1

Take three cardboards A, B and C and make a pinhole at their centers. Place a burning candle on one side of A and arrange the cardboards in such a way that the three pinholes and the candle flame are in a straight line. The candle flame will be visible through the pinhole of the cardboard C. Now slightly displace any one of the cardboards and try to see the flame through the pinhole of the cardboard C. The flame will not be visible. From this it is clear that light travels in a straight line.

In a homogenous transparent medium, light travels in a straight line and this is known as rectilinear propagation of light. This can be demonstrated by the following experiment.

Answer 2

RECTILINEAR PROPERTY OF LIGHT

1)According to FERMAT'S PRINCIPLE,

light takes the path that takes the minimum time to traverse.

2)Generally light chooses the straight path which is the shortest path connecting any two points according to euclidean geometry.

Experiment

1)Take one candle and 3 cardboards for the experiment

2)Then place them in a line as shown in the attachment.

3)Make 3 holes in cardboard such that the holes are in same line with the candle as in the attachment shown above.

4)Light up the candle and see the light thought the holes. You will see that it is coming in a straight line and is clearly visible.

5)Then move any one of the cardboard slightly from it's postition and then you will see that you can't observe the light that was earlier visible as the 3 holes were not in straight line now.

THIS PROVES LINE TRAVELS IN A STRAIGHT LINE.

thanks