Light

Light reflection occurs when a ray of light bounces off a surface and changes direction. From a detailed definition of ‘reflection of light’ to the different types of reflection and example images, our introductory article tells you everything you need to know about the reflection of light.

Reflection of Light

Reflection of light (and other forms of electromagnetic radiation) occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface.

Example

The simplest example of visible light reflection is the surface of a smooth pool of water, where incident light is reflected in an orderly manner to produce a clear image of the scenery surrounding the pool. Throw a rock into the pool, and the water is perturbed to form waves, which disrupt the reflection by scattering the reflected light rays in all directions.

Because light behaves in some ways as a wave and in other ways as if it were composed of particles, several independent theories of light reflection have emerged. According to wave-based theories, the light waves spread out from the source in all directions, and upon striking a mirror, are reflected at an angle determined by the angle at which the light arrives. The reflection process inverts each wave back-to-front, which is why a reverse image is observed. The shape of light waves depends upon the size of the light source and how far the waves have traveled to reach the mirror. Wavefronts that originate from a source near the mirror will be highly curved, while those emitted by distant light sources will be almost linear, a factor that will affect the angle of reflection.

According to particle theory, which differs in some important details from the wave concept, light arrives at the mirror in the form of a stream of tiny particles, termed photons, which bounce away from the surface upon impact. Because the particles are so small, they travel very close together and bounce from different points, so their order is reversed by the reflection process, producing a mirror image. Regardless of whether light is acting as particles or waves, the result of reflection is the same. The reflected light produces a mirror image.

The amount of light reflected by an object, and how it is reflected, is highly dependent upon the degree of smoothness or texture of the surface. When surface imperfections are smaller than the wavelength of the incident light (as in the case of a mirror), virtually all of the light is reflected equally. However, in the real world most objects have convoluted surfaces that exhibit a diffuse reflection, with the incident light being reflected in all directions. Many of the objects that we casually view every day (people, cars, houses, animals, trees, etc.) do not themselves emit visible light but reflect incident natural sunlight and artificial light. For instance, an apple appears a shiny red color because it has a relatively smooth surface that reflects red light and absorbs other non-red (such as green, blue, and yellow) wavelengths of light.