Question

1) If we have a broad source of light, and we put something in-front of it, why do we get a diffused shadow? And if we have a point source of light why does the shadow gets sharpened? Please explain the phenomenon too.

2) This is a similar question, lets say we make a "+" shaped small cut on a paper so that we can pass sunlight through it and observe its projection on a screen behind. If that screen is close to the "+" shaped opening, the projection is a distinct "+" sign. But as we move the screen away, why does the projected beam of sunlight always takes the shape of a circle. (Even in the case of "rectangle" shaped opening or "triangle".)

Answer 1