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Snell's law (also known as the Snell–Descartes law, the ibn-Sahl law, [1] and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.
Let the angle of refraction, measured in the same sense, be θ t, where the subscript t stands for transmitted (reserving r for reflected). In the absence of Doppler shifts, ω does not change on reflection or refraction. Hence, by , the magnitude of the wave vector is proportional to the refractive index.
where R is the radius of the spherical surface, n 2 is the refractive index of the material of the surface, n 1 is the refractive index of medium (the medium other than the spherical surface material), is the on-axis (on the optical axis) object distance from the line perpendicular to the axis toward the refraction point on the surface (which ...
where is the index of refraction at the center of the lens and is the radius of the lens's spherical surface. [6] The index of refraction at the lens's surface is n 0 / 2 {\displaystyle n_{0}/2} . The lens images each point on the spherical surface to the opposite point on the surface.
Visulization of flux through differential area and solid angle. As always ^ is the unit normal to the incident surface A, = ^, and ^ is a unit vector in the direction of incident flux on the area element, θ is the angle between them.
A spherical lens has an aplanatic point (i.e., no spherical aberration) only at a lateral distance from the optical axis that equals the radius of the spherical surface divided by the index of refraction of the lens material. Spherical aberration makes the focus of telescopes and other instruments less than ideal. This is an important effect ...
Wave refraction in the manner of Huygens Wave diffraction in the manner of Huygens and Fresnel. The Huygens–Fresnel principle (named after Dutch physicist Christiaan Huygens and French physicist Augustin-Jean Fresnel) states that every point on a wavefront is itself the source of spherical wavelets, and the secondary wavelets emanating from different points mutually interfere. [1]
where n is the index of refraction of the medium in which the lens is working (1.00 for air, 1.33 for pure water, and typically 1.52 for immersion oil; [1] see also list of refractive indices), and θ is the half-angle of the maximum cone of light that can enter or exit the lens.