Although these analogies are not necessarily incorrect, the above definition is slightly more mathematically rigorous in the context of classical electromagnetics. To be sure, it is sometimes easier to imagine a ray as, for instance, a "ray" of sunlight or a laser beam. This direction of travel, because it is uniform all across the plane wave, is called a ray. The diagram below shows a plane wave in two dimensions. For a so-called plane wave, all we need to know is the direction of travel, since the wave has a constant magnitude over the plane perpendicular to the direction. At a sufficiently large distance, the radius of the circle becomes so large that the wave appears (locally) as a line rather than a curve (in three dimensions, the wave appears to be a plane). Notice that as the waves get farther away from the source, the curvature of the circle decreases. The diagram below shows the waves moving outward from the source. The waves radiate symmetrically from the particle in concentric circles. Imagine electromagnetic radiation (light) emanating from a charged particle far away. O Use the law of refraction to describe the "bending" of rays as the pass from one material to another O Define the index of refraction and its relationship with material parameters O Use the law of reflection to calculate the direction of reflected rays O Describe the relationship between a wave and a ray To try - the answers are given to you.In this article, we introduce the concept of a ray and discuss the laws of reflection and refraction. This equation 'n' is quoted for rays going from the rare optical medium Of the critical angle = the refractive indexĭense to an optically rare medium so the result will be <1 Sine of 90 o is 1 so the equation becomes: Is called the critical angle and is given the symbol 'c'. The angle of refraction is 90 o then the angle of incidence Speed of the wave as it crosses into the new medium before you start the maths. The angle of incidence and therefore the ratio will equal a value greaterĪlways sort out in your mind what is happening to the Remember - if it slows down the the angle of refraction will be smaller than To the ration of the speeds of the waves through the media. The ratio of the sines of the angles is equal That the ratio of the two will produce a constant value that we call Is directly proportional to the sine of the angle of refraction and This indicates that the sine of the angle of incidence The sine of the angle of refraction you get a straight line that goes You will find that if you plot the sine of the angle of incidence against Occur - look carefully at the basic refraction page and follow the linkĪn experiment and measure the angle of incidence and the angle of refraction Talking about sound - remember is is the SPEED CHANGE that makes refraction Of OPTICAL media on this page - but there is nothing to stop the examiners You simply find the reciprocal (see interactive 'n' is equal to the ratio of the 'wavespeed' before and after it crosses the boundary.ġn 2 is the inverse of 2n 1. This is equivalent to the ratio of phase velocities in the two media (expressed as v or c), or equivalent to the reciprocal of the ratio of the indices of refraction. Media is a constant termed the refractive index - n - (which is the ratio of the indices of refraction). Of refraction of a wave as it travels through a boundary between two Law states that the ratio of the angle of incidence to the angle Relationship to the observations of refraction made at GCSE. A Level and AS level - UK KS 5 (Age 16 - 18).GCSE and 'O' Level - UK KS4 (Age 14 - 16).
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