There are several everyday phenomena that demonstrate the straight-line propagation of light. Here are four common examples:
Shadows: When an object blocks a source of light, it creates a shadow on the opposite side. Shadows form because light travels in straight lines, and when an object obstructs the path of light, it cannot reach the area behind the object, resulting in a dark shadow.
Formation of images by mirrors: Mirrors reflect light in a predictable manner, obeying the law of reflection. When light rays strike a mirror, they bounce off at the same angle they hit the mirror's surface. This behavior allows mirrors to form clear, undistorted images by reflecting light rays in straight lines.
Straight path of laser beams: Laser pointers or laser beams are often used to illustrate the straight-line nature of light. A laser produces a narrow and coherent beam of light that propagates in a straight line until it encounters an obstacle or medium that alters its path. This property makes lasers useful in applications such as alignment, surveying, and optical communication.
Formation of sharp shadows in sunlight: On a sunny day, objects outdoors can cast well-defined shadows. The sharpness of these shadows is a result of the sun's rays traveling in nearly parallel lines due to the Sun's large distance from Earth. Since sunlight essentially consists of parallel rays, objects cast sharp shadows when they intercept these straight rays.
These are just a few examples that highlight the straight-line propagation of light in everyday situations. The behavior of light in these phenomena is consistent with the principle of light traveling in straight lines, known as rectilinear propagation.