The behavior of waves, whether they are sound waves or light waves, when encountering objects is determined by the interaction of the waves with the object's size, shape, and material properties. The difference in behavior between sound and light in this context can be attributed to the fundamental differences between their properties.
When sound encounters an object that is much larger than its wavelength, it undergoes a phenomenon called diffraction. Diffraction occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. The sound wave bends around the edges of the object and spreads out into the region behind the obstacle. This bending and spreading of sound waves allow them to "wrap around" objects and reach areas that would otherwise be shadowed.
In the case of light, its wavelength is typically much smaller than the size of everyday objects. When light encounters an object that is larger than its wavelength, it interacts with the object primarily through scattering and absorption processes. If the object is transparent or translucent, the light can pass through it relatively unimpeded, with only minor scattering and absorption effects. This is why we often perceive light as passing through objects like glass or air.
However, if the object is opaque or if the light encounters a surface that is rough or irregular at a scale comparable to its wavelength, the light can be reflected or scattered in various directions, leading to the appearance of reflection. This is why we see light being reflected by surfaces like mirrors or metals.
In summary, the different behaviors of sound and light waves when encountering objects can be attributed to the differences in their wavelength, the size of the objects, and the nature of their interactions with the object's material properties.