Images of diffraction of sound4/4/2024 The side view would be a graph of the electric or magnetic field. From above, we view the wave fronts (or wave crests) as if we were looking down on ocean waves. A light wave can be imagined to propagate like this, although we do not actually see it wiggling through space. Huygens’s principle is an indispensable tool for this analysis.įigure 1.25 shows how a transverse wave looks as viewed from above and from the side. This is particularly true when the wavelength is not negligible compared to the dimensions of an optical device, such as a slit in the case of diffraction. However, some phenomena require analysis and explanations based on the wave characteristics of light. So far in this chapter, we have been discussing optical phenomena using the ray model of light. Use Huygens’s principle to explain diffraction.Use Huygens’s principle to explain the law of refraction.Use Huygens’s principle to explain the law of reflection.But, as the angle of incidence approaches 90°, the apparent depth approaches zero, albeit reflection increases, which limits observation at high angles of incidence.By the end of this section, you will be able to: įor small angles of incidence (measured from the normal, when sin θ is approximately the same as tan θ), the ratio of apparent to real depth is the ratio of the refractive indexes of air to that of water. The opposite correction must be made by an archer fish. Conversely, an object above the water has a higher apparent height when viewed from below the water. This is an important consideration for spearfishing from the surface because it will make the target fish appear to be in a different place, and the fisher must aim lower to catch the fish. The depth that the water appears to be when viewed from above is known as the apparent depth. This causes the pencil to appear higher and the water to appear shallower than it really is. The lines of sight (shown as dashed lines) intersect at a higher position than where the actual rays originated. Once the rays reach the eye, the eye traces them back as straight lines (lines of sight). This is due to the bending of light rays as they move from the water to the air. Looking at a straight object, such as a pencil in the figure here, which is placed at a slant, partially in the water, the object appears to bend at the water's surface. Refraction occurs when light goes through a water surface since water has a refractive index of 1.33 and air has a refractive index of about 1. On water A pencil part immersed in water looks bent due to refraction: the light waves from X change direction and so seem to originate at Y. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed.įor light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence θ 1. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. The redirection can be caused by the wave's change in speed or by a change in the medium. In physics, refraction is the redirection of a wave as it passes from one medium to another. Not to be confused with Diffraction, the change in direction of a wave around an obstacle.Ī ray of light being refracted in a plastic block
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