Question

explain interference and diffraction? how the wave nature of light can explain this?

Answer 1

These related phenomena are best explained through diagrams. I would recommend googling the images. The ideas at their basic level, though, are not too complex.
Firstly, one must understand what it means that light behaves like a wave. Given that mathematical knowledge, if two identical, yet opposite wave functions are superimposed upon (added to) each other, then they will cancel out precisely. This property can most easily be related to in regards to the wave a drop of water created when dropped into a pool. Diffraction does just this. When light is sent through an obstacle such as a pinpoint in a wall, it creates a 'ripple' of light into the new space that it is encountering, much like our drop of water.
If you would like to see the effects for yourself, take a tub or a pool and spill two drops of water simultaneously a respectable distance from each other. You will see that where they meet, the properties of interference will hold and the like waves will complement each other. You may also notice that the waves seamlessly flow through each other as well; they do not remove any momentum from their surrounding waves, nor vise versa.

Answer 2

These related phenomena are best explained through diagrams. I would recommend googling the images. The ideas at their basic level, though, are not too complex. Firstly, one must understand what it means that light behaves like a wave. Given that mathematical knowledge, if two identical, yet opposite wave functions are superimposed upon (added to) each other, then they will cancel out precisely. This property can most easily be related to in regards to the wave a drop of water created when dropped into a pool. Diffraction does just this. When light is sent through an obstacle such as a pinpoint in a wall, it creates a 'ripple' of light into the new space that it is encountering, much like our drop of water. If you would like to see the effects for yourself, take a tub or a pool and spill two drops of water simultaneously a respectable distance from each other. You will see that where they meet, the properties of interference will hold and the like waves will complement each other. You may also notice that the waves seamlessly flow through each other as well; they do not remove any momentum from their surrounding waves, nor vise versa.