Listening Part 4: Highlight correct summary

PTE Listening Part 4- Sample 8: Highlight Correct Summary

Shadow is the dark real image which forms when light from a source is blocked by an opaque object occupying the complete three-dimensional volume behind an object which has light in front of it. A simple shadow is known as an umbra but when the source of light is extended, the shadow gets divided into umbra, penumbra, and antumbra. In the latter case, the shadow is also blurry and when two or more shadows merge or are about to merge, they create an effect called shadow blister. The darkest shadow range is the umbra region, which does not receive any direct light, contrary to which in the penumbra region, the light is though less intense but can enable viewing the light source.