Which term describes the region of a shadow where the light source is completely blocked?

• A. Penumbra
• B. Umbra
• C. Doldrums
• D. Cohesion

Answer: (B)

The region of a shadow where the light source is completely blocked is called the umbra. In this zone no light from the source reaches, so the shadow appears full and dark. When the light source is extended rather than a single point, there’s also a surrounding area called the penumbra, where only part of the light is blocked and the shadow is lighter. The other terms describe unrelated ideas: doldrums are calm, windless regions near the equator in the atmosphere, and cohesion is a property of how particles stick together. A helpful example is a solar eclipse: inside the umbra you’d see a total eclipse, while in the penumbra you’d see a partial eclipse.