1. Shadows: Shadows are formed when an object blocks light. The shape of the shadow directly corresponds to the shape of the object, and the shadow is cast in a straight line away from the object. If light traveled in a curved or random path, shadows would be distorted and irregular.
2. Pinhole Camera: A pinhole camera is a simple device with a tiny hole that allows light to enter and create an image on the opposite wall. The image formed is always an inverted projection of the object, which would not be possible if light traveled in a non-straight line. The sharpness of the image also supports this, as any curve in the light path would blur the image.
