Light travels in a straight line through an homogenous
medium. It can be proved by an experiment given below.

Arrange two pieces of cardboard, having pin holes at the
centre of each, vertically, one behind the other. They
should be arranged in such a way that the two holes are
exactly in the same level with each other. Now place a
candle behind and in level with the hole of the second
cardboard. It will be visible when viewed through the hole
of the first cardboard. Now displace one of the cardboards
slightly to its life or right candle would no longer be
visible. This shows that light travels in a straight line.

Rectilinear Propagation of Light is the tendency of light 
to only travel in straight lights.

This means that if light "criss-crosses" between each other 
whilst going through a small hole, you will see the image 
upside down, as the light goes straight up from down, and 
down from up.

Consider a path of light is entering to a dark room through 
a narrow slit in a window, illuminated by sunlight.it will  
be in straight.But if an obstacle is placed in the path of 
light,A sharp shadow will cast on the screen showing that 
light travels in straight line. I think this is RECTILINEAR 
PROPAGATION OF LIGHT.........But it has been observed 
that,If the obstacle placed is very small some light 
encroaches into the geometrical shadow.This will occur if 
light is able to bend round the edges of the obstacle.this 
happens only if light travels in the form of waves.

Light travels in a straight line as long as it is 
travelling through the same medium, this is called the 
rectilinear propagation of light.

In a homogeneous transparent medium light travels in a
straight line and this is known as rectilinear propagation
of light.

in a homonogenious transparent medium light travels in a
straight line. This is known as rectilinear propagation of
light.

Arrange two pieces of cardboard, having pin holes at the
centre of each, vertically, one behind the other. They
should be arranged in such a way that the two holes are
exactly in the same level with each other. Now place a
candle behind and in level with the hole of the second
cardboard. It will be visible when viewed through the hole
of the first cardboard. Now displace one of the cardboards
slightly to its life or right candle would no longer be
visible. This shows 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:
 
Take three cardboards A, B and C and make a pinhole at 
their centres. Place a burning candle on one side of the 
cardboard 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.

Light travells in a straight line.This mode of travelling 
is called Rectilinear Propagation of Light.

rectilinear propagation of light means that light traveling
in straight line without being interrupted in between.

Straight line travel. This denotes the fact that Light 
travels in a straight line when traveling through a medium 
with a constant refractive index.


its very simple.. :D 

Light can easily travel in straight line..

Light travells in a straight way.
We can see a candle's flame by looking through a straight 
pipe,but cant see if the pipe is bended.
So we could define light travells i straight way and this 
is called Rectilinear propagation of light.

Source of light, the object and its shadow all are in a
straight line as light travels in a straight line which is
called as Rectilinear Propagation of light.