Explain why light travels in a straight line and how it affects the formation of shadows.

When you place an opaque object (like a book) in the path of light, it blocks all the light rays from passing through it. This is because the object does not let light go through it. Since light travels in straight lines, it can't bend around the object. This means no light reaches the space behind the object, and thus, a shadow is formed.

Light travels in straight lines because it moves in a direct path from its source. It doesn’t change direction easily unless it hits something, like an object or a surface. Because of this, when light meets an opaque object, it can't bend around it or go through it, so the area behind the object stays dark, creating a shadow.