√ Reflection - World Communicates - Preliminary Physics - iitutor

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• published: 08 Oct 2013
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https://www.iitutor.com Reflection is when waves, such as water waves, sound and light fall on objects they can bounce off the object. This bouncing off is called reflection. Light reflected from a smooth surface obeys the following law of reflection. The incident ray, reflected ray and normal are always in the same plane. The frequency and wavelength of the reflected wave are identical to the frequency and wavelength of the incident wave. A mirror is a highly reflecting smooth surface, often consisting of a glass sheet with a 'silver' backing. Rays of light reflect from the mirror according to the laws of reflection stated above. When we look into a plane mirror we view an image of ourselves. Plane mirrors are used in a diverse range of human endeavour including household mirrors, in submarine periscopes and in sextants for navigation. A rotating mirror drum is found in bar scanners at supermarkets and libraries and there are retro¬-e lectors used in vehicles and road signs. If a wave encounters a rough boundary, it will be reflected in many directions. This type of reflection is called diffuse reflection and is the type of reflection that allows us to see the objects around us. Light reflected from a smooth surface is said to undergo specular reflection. Whether a surface is rough or not depends on the wavelength of the light being reflected. A surface is considered to be smooth if the difference in the elevations in the surface is less than one-eighth of the incident wave's wavelength. Hence a surface may appear smooth for some wavelengths and rough for others. Light reflected from a rough surface can be viewed from any direction, while light reflected from a smooth surface can only be viewed from one direction. This is why it is possible to read this page, which is rough for visible light, from any direction. For any ray from a point source we can construct a ray diagram involving reflection from a plane reflective surface by following three simple steps. Firstly, Draw the surface and the normal to that surface. Secondly, Draw the incident ray as an arrow toward the surface at the angle of incidence. Lastly, draw the reflected ray as an arrow pointing away from the surface at the angle of reflection, remembering that the angle of incidence equals the angle of reflection. PB2411 http://youtu.be/2LA0-NVt208