What are the condition in which light will behave as a,wave particles or ray
So, you must not try to decide between these two. Light has these characteristics embedded within it.
Now, the matter of concern is why or what causes light to behave differently in different cases.
In the double slit interference experiments with light and matter particles, we can see that only when the size of slits are comparable to wavelength of light/matter wave, they show typical wave phenomena. On a much larger scale, however, they show particle nature.
Hope this helps :)