F. When an opaque object is placed in the pathway of a beam of light, a shadow is made.
1. A shadow is the area behind the opaque object where light is blocked
2. The closer an object is to the light source, the larger the shadow, because it is blocking more light
3. The darkest part of the shadow where the light is completely blocked (from transmitting through the object), is called the umbra
a. The umbra is not absolutely dark because scattered light makes its way into the shadow
4. The fuzzy part of the shadow between the umbra and the light is called the penumbra
a.The penumbra occurs because the light source sends out light from different points
i. Some, but not all, of the original light is blocked (or subtracted)
ii. As light is subtracted, the light becomes dimmer
If the light sources is distant, like the sun, the light comes in parallel rays and makes sharp shadows. If you have a small light source, like a very small flashlight, the penumbra is relatively small. If you have a large light source, the rays are coming at the object from a wider area, which creates a larger penumbra.
- If an opaque object blocks the light from transmitting through, causing a shadow, why then can you still see objects behind the shadow? (HINT: You need to think about all the things you've learned about light so far.)