2020 · Q105
Which one of the following combinations of source and screen would produce sharpest shadow of an opaque object?
General KnowledgePhysics
- AA point source and an opaque screen
- BAn extended source and an opaque screen
- CA point source and a transparent screen
- DAn extended source and a transparent screen
Explanation
The sharpest shadow requires a point source — an extended source creates a blurred penumbra — and an opaque screen, since a transparent screen would not show a sharp shadow. This is why a small, intense bulb held close to an object casts a crisper shadow than a tube light. A point source paired with an opaque screen gives the sharpest shadow.