Activity
Take three cardboard X, Y and Z make a very small hole at their centre. Place 3 cardboard in such manner light will be passing through it. Now take a candle and placed at in front of X cardboard and take one white paper and place in front of Z cardboard as screen. Now burn the candle and note down your observations. When light ray of candle is passing through a X, Y and Z hole, this light ray is incident on a screen.
This ray traveling through a small hole in straight manner. When light ray travel in straight path is called as rectilinear propagation of light.
Rectilinear propagation of light is the principle that state that light travel in
a straight line in a homogeneous medium as long as it is not reflected.