There is a shadow of a house stretching across the back yard. Why is the part of the shadow closest to the house sharper than the part further away?

There is a shadow of a house stretching across the back yard. Why is the part of the shadow closest to the house sharper than the part further away?

• A. Because the shadow closest to the house is closer to the object producing the shadow
• B. Because the sun angle changes near the house
• C. Because the ground texture varies near the house
• D. Because the house blocks more light near itself

Answer: (A)

The sharpness stem from how shadows form with a real, extended light source. The sun isn’t a single point of light; it has a small angular size. That means rays come from a range of directions. Right next to the house, the shadow region is fully blocked by the house, so the boundary is very crisp—the edge lies in full umbra. As you move farther away, some light from the sun can graze around the edges of the house, so the boundary blurs into a softer edge (the penumbra). In short, the part of the shadow closest to the house is sharper because it sits in the region where all light is blocked, while farther away the finite size of the sun lets some light through around the edges.

The sharpness stem from how shadows form with a real, extended light source. The sun isn’t a single point of light; it has a small angular size. That means rays come from a range of directions. Right next to the house, the shadow region is fully blocked by the house, so the boundary is very crisp—the edge lies in full umbra. As you move farther away, some light from the sun can graze around the edges of the house, so the boundary blurs into a softer edge (the penumbra). In short, the part of the shadow closest to the house is sharper because it sits in the region where all light is blocked, while farther away the finite size of the sun lets some light through around the edges.