Aerogel is a very low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Almost all solids and liquids have refractive indices above 1.3, with aerogel as the clear exception. Gases at atmospheric pressure have refractive indices close to 1 because of their low density. These values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, as is conventionally done. A few examples are given in the adjacent table. PMMA (acrylic, plexiglas, lucite, perspex)įor visible light most transparent media have refractive indices between 1 and 2. Selected refractive indices at λ = 589 nm.įor references, see the extended List of refractive indices. Where the coefficients A and B are determined specifically for this form of the equation. The relative refractive index of an optical medium 2 with respect to another reference medium 1 ( n 21) is given by the ratio of speed of light in medium 1 to that in medium 2. Such lenses are generally more expensive to manufacture than conventional ones. įor lenses (such as eye glasses), a lens made from a high refractive index material will be thinner, and hence lighter, than a conventional lens with a lower refractive index. In this case, the speed of sound is used instead of that of light, and a reference medium other than vacuum must be chosen. It can also be applied to wave phenomena such as sound. The concept of refractive index applies across the full electromagnetic spectrum, from X-rays to radio waves. Nevertheless, refractive indices for materials are commonly reported using a single value for n, typically measured at 633 nm. For most materials the refractive index changes with wavelength by several percent across the visible spectrum. The imaginary part then handles the attenuation, while the real part accounts for refraction. Light propagation in absorbing materials can be described using a complex-valued refractive index. This effect can be observed in prisms and rainbows, and as chromatic aberration in lenses. This causes white light to split into constituent colors when refracted. The refractive index may vary with wavelength. This implies that vacuum has a refractive index of 1, and assumes that the frequency ( f = v/ λ) of the wave is not affected by the refractive index. The refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is v = c/ n, and similarly the wavelength in that medium is λ = λ 0/ n, where λ 0 is the wavelength of that light in vacuum. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the critical angle for total internal reflection, their intensity ( Fresnel's equations) and Brewster's angle. This is described by Snell's law of refraction, n 1 sin θ 1 = n 2 sin θ 2, where θ 1 and θ 2 are the angle of incidence and angle of refraction, respectively, of a ray crossing the interface between two media with refractive indices n 1 and n 2. The refractive index determine how much the path of light is bent, or refracted, when entering a material. In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. In as few words as possible describe the 4 phenomenon all waves have.Ratio of the speed of light in vacuum to that in the medium A ray of light being refracted through a glass slab.How many nodes and antinodes does this standing wave have?.What is true about the wavelength of a standing wave with a lower frequency?.Draw and label (node and antinode) of a standing wave with 3 nodes and 2 antinodes.A standing waves reflection must be the same _.Finish off table by drawing the waves interacting during and after their interference.How are they similar? How are they different? Compare and contrast constructive and destructive interference.Why can waves travel through each other and not collide?.Is light bending toward or away from the normal line (on the air side) when you look at a fish in water where light travels slower?.If a ray of light were traveling from Air to water at a 30° angle of incidence, would its angle of refraction be more than 30°, less than 30°, or equal to 30° on the water side?.If an incident wave has an angle of incidence of 35°, what would be the angle of reflection?.Draw and label a diagram for reflection of a wave.Describe what happens to the wave after it bounces off a fixed boundary.Describe what happens to the wave after it bounces off a flexible boundary.
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