Light rays generally travel in straight lines in a homogeneous medium, such as air or a vacuum. This behavior is known as rectilinear propagation. When light encounters an obstacle or a different medium, it can exhibit several wave phenomena, including reflection, refraction, diffraction, and interference. These phenomena can cause the path of light to deviate from a straight line.
Reflection: When light encounters a smooth surface, such as a mirror, it undergoes reflection, bouncing off the surface at an angle equal to the angle of incidence. This is why you can see your reflection in a mirror.
Refraction: Refraction occurs when light passes from one medium to another with a different refractive index. The change in speed and direction causes the light to bend. For example, when light passes from air to water, it refracts and changes direction.
Diffraction: Diffraction refers to the bending or spreading of light as it encounters an obstacle or passes through a narrow opening. It occurs when light waves encounter an object or aperture that is comparable in size to their wavelength. This phenomenon is observable when light waves pass through narrow slits or around obstacles, causing the light to spread out and create interference patterns.
Interference: Interference is the interaction of multiple light waves, resulting in constructive or destructive interference patterns. This phenomenon occurs when two or more coherent light sources overlap, causing reinforcement or cancellation of certain parts of the waves. It can result in patterns of bright and dark regions, such as in the case of interference in thin films or diffraction gratings.
Therefore, while light rays typically travel in straight lines in a uniform medium, they can be affected by reflection, refraction, diffraction, and interference when encountering obstacles or different media. These wave phenomena contribute to the complex behavior of light and allow for a variety of optical phenomena and applications.