Why does the shadow of an object become more crisp and sharp when the object is closer to the screen/farther from the light source?
In: Physics
Because the light source is larger than a point. The bigger the light source, the blurrier its shadows will be. With shadows there’s an area that can’t see any of the light and another that can see all of the light. In between there’s an area that has part of the light hidden by the shading object and part of the light visible. That in-between area is what makes up the blurry part of the shadow. The closer the shading object is to the shadow, the smaller the in-between area will be, just due to geometry.
The totally shaded region is called the umbra and the partly-shaded, in-between area is called the penumbra. These terms are often used for solar eclipses. If you see the sun completely covered by the moon, during totality, you’re in the umbra. During the partial part of the eclipse you’re in the penumbra and can see only part of the sun.
This is very vaguely worded so it’s kind of hard to tell what you’re wanting to know/what situation you’re imaging. What’s important to note is that light isn’t just a beam that starts at the source and ends when it hits something. Light is always reflected (talking about everyday situations here) which causes diffused ambient light which softens shadows.
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