Question

What is rectilinear propagation of light? How will you prove it?

Answer 1

Rectilinear propagation of light is the name given to the property that light travels in a straight line.
To prove this property of light, we'll perform the following activity:


Take a candle and a rubber pipe (bendable)

Burn the candle with a matchstick, and holding the pipe in the line of the level of candle, try to see the flame from another side.

Now, bend the rubber pipe, and try to see the flame again.




OBSERVATIONS:



We observe that the flame is only visible if the pipe is held straight, and not when the pipe is bent, hence, proved.

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