Key Stage 3 (KS3) Physics Practice Test

Light travels in a straight line when it moves through a uniform medium, such as air or a vacuum. This principle is rooted in the nature of light as an electromagnetic wave; it moves in predictable paths unless it encounters a change in medium or is influenced by gravitational fields or other forces.

This straight-line motion is observable in various phenomena, such as the way shadows are formed or how we see objects. For example, when you hold an object in front of a light source, the light travels in a straight path from the source, creating a shadow of the object on the surface behind it.

In contrast, other options suggest different paths. A circular path would imply that light is bending continuously around a loop, which is not the case in free space. Zigzag patterns would suggest interruptions in its motion, which doesn’t typically happen under normal conditions. A curved path can occur in specific circumstances, like when light passes through a lens or is affected by gravitational fields, but it does not represent the default behavior of light in a uniform medium. Thus, the correct answer highlights the fundamental behavior of light traveling in a straight line under typical conditions.