Regular reflection differs from diffuse reflection because, in diffuse reflection, the reflected rays tend to scatter away from the surface. According to the law of reflection, the light that encounters a boundary is affected by the optical and electronic response functions of the material towards the electromagnetic radiation. During regular reflection, the light reflects and arrives at the same angle. We can experimentally show the difference between regular reflection and disuse reflection by coating a surface with glossy paint and matte paint; the matte paint mainly shows the specular reflection behavior, while the surface with glossy paint mainly shows diffuse reflection.
Some examples of regular reflection include visible light on a mirror, radio waves, and microwaves on flying objects, acoustic mirrors reflects sound and atomic mirrors reflect neutral atoms. Diffuse reflection refers to the reflection of light or other waves from a surface through the scattering effect.
In other words, in diffuse reflection, the waves are reflected from a surface in such a way that the incident ray is scattered at many angles. In contrast, in regular reflection, there is a single angle at which the incident ray reflects. In an ideal diffuse reflection process, we can observe Lambertian reflection there is equal luminance upon viewing from all the directions that are lying at a half-space that is adjacent to the surface. Some examples of materials that can cause diffuse reflection include plaster non-absorbing powder , paper made of fibers , and white marble polycrystalline.
Generally, regular reflection does not happen in these materials due to surface roughness. Similarly, a flat surface does not always provide specular reflection. Normally a roadway would cause diffuse reflection due to its rough surface. But if the surface is wet, water can fill in the crevices and smooth out the surface.
Rays of light from the beam of an oncoming car hit this smooth surface, undergo specular reflection and remain concentrated in a beam. The driver perceives an annoying glare caused by this concentrated beam of reflected light. A second application of the distinction between diffuse and specular reflection pertains to the field of photography.
Many people have witnessed in person or have seen a photograph of a beautiful nature scene captured by a photographer who set up the shot with a calm body of water in the foreground. The water if calm provides for the specular reflection of light from the subject of the photograph.
Light from the subject can reach the camera lens directly or it can take a longer path in which it reflects off the water before traveling to the lens. Since the light reflecting off the water undergoes specular reflection, the incident rays remain concentrated instead of diffusing.
The light is thus able to travel together to the lens of the camera and produce an image an exact replica of the subject which is strong enough to perceive in the photograph.
An example of such a photograph is shown below. If a bundle of parallel incident rays undergoing diffuse reflection follow the law of reflection, then why do they scatter in many different directions after reflecting off a surface? Each individual ray strikes a surface which has a different orientation. Since the normal is different for each ray of light, the direction of the reflected ray will also be different.
Perhaps you have observed magazines which have glossy pages. The usual microscopically rough surface of paper has been filled in with a glossy substance to give the pages of the magazine a smooth surface. Do you suppose that it would be easier to read from rough pages or glossy pages? Explain your answer. It is much easier to read from rough pages which provide for diffuse reflection. Glossy pages result in specular reflection and cause a glare.
The reader typically sees an image of the light bulb which illuminates the page. Without it, we would not have cameras or mirrors. However, diffuse reflection that is central to our ability to see the world. Aside from the limited number of luminous objects, such as light bulbs and the sun, everything we see around us is visible because of diffuse reflection.
Test your understanding of the concepts covered with the specular vs diffuse reflection problem set. Follow SciencePrimer. Skip to main content. Subject tag:. Search form. Subscribe to our YouTube Channel:. Follow SciencePrimer Tweet. Contact SciencePrimer. Langmuir Circulation.
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