justify and explain this

its a urgent question

1- the fact that a small source of light cast a sharp shadow of an opaque object tells us that light travels in straight line path i dont understand this

2- how and why ddoes any object caste shadow

3- what is the evidence for wave nature of light as well as for particle nature of light

4- explain this line in 150 words and prove this

light is composed of particles which travels in a straight line at very high speed

 1).   Light travels in a straight line. This can be proved in the experiment when we can see a lighted candle through a pipe only when it is kept straight. Otherwise if we bend the pipe, we can't see the candle.

 2).  A shadow is cast when light rays are stopped by an opaque object. The light which does not reach the object continue to pass while some of it is stopped by the object. That is why a dark region is formed which is called a shadow.

3). Light behaves in a wave form when it passes through a very small opaque object.  Then light has a tendency to bend around the object and not to pass straight. This is called diffraction of light.

4).  So light behaves both as particles and as a wave. As a wave when diffraction occurs and as particles normally.

HOPE THIS HELPS