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Prentice's rule, named so after the optician Charles F. Prentice, is a formula used to determine the amount of induced prism in a lens: = where: P is the amount of prism correction (in prism dioptres) c is decentration (the distance between the pupil centre and the lens's optical centre, in millimetres)
After simplifying the final equation is found: F F c = 1 − x F ⇒ F c = F 1 − x F = 1 1 F − x ⇒ F = 1 1 F c + x {\displaystyle {\begin{aligned}&&{\frac {F}{F_{\text{c}}}}&=1-xF\\&\Rightarrow &F_{\text{c}}&={\frac {F}{1-xF}}={\frac {1}{{\frac {1}{F}}-x}}\\&\Rightarrow &F&={\frac {1}{{\frac {1}{F_{\text{c}}}}+x}}\end{aligned}}}
In the above formula for r s , if we put = / (Snell's law) and multiply the numerator and denominator by 1 / n 1 sin θ t , we obtain r s = − sin ( θ i − θ t ) sin ( θ i + θ t ) . {\displaystyle r_{\text{s}}=-{\frac {\sin(\theta _{\text{i}}-\theta _{\text{t}})}{\sin(\theta _{\text{i}}+\theta _{\text{t}})}}.}
Esophoria is an eye condition involving inward deviation of the eye, usually due to extra-ocular muscle imbalance. It is a type of heterophoria. Cause. Causes include: Refractive errors; Divergence insufficiency; Convergence excess; this can be due to nerve, muscle, congenital or mechanical anomalies.
Amblyopia. Anisometropia is a condition in which a person's eyes have substantially differing refractive power. [1] Generally, a difference in power of one diopter (1D) is the threshold for diagnosis of the condition . [2] [3] Patients may have up to 3D of anisometropia before the condition becomes clinically significant due to headache, eye ...
The most general form of Cauchy's equation is. where n is the refractive index, λ is the wavelength, A, B, C, etc., are coefficients that can be determined for a material by fitting the equation to measured refractive indices at known wavelengths.
Lorentz transformation. The following notations are used very often in special relativity: Lorentz factor. where and v is the relative velocity between two inertial frames . For two frames at rest, γ = 1, and increases with relative velocity between the two inertial frames. As the relative velocity approaches the speed of light, γ → ∞.
This gives an angular correction = / ≈ 0.000099364 rad = 20.49539 sec, which can be solved to give = / = ≈ 0.000099365 rad = 20.49559 sec, very nearly the same as the aberrational correction (here is in radian and not in arcsecond).
The free air correction is calculated from Newton's Law, as a rate of change of gravity with distance: g = G M R 2 d g d R = − 2 G M R 3 = − 2 g R {\displaystyle {\begin{aligned}g&={\frac {GM}{R^{2}}}\\{\frac {dg}{dR}}&=-{\frac {2GM}{R^{3}}}=-{\frac {2g}{R}}\end{aligned}}}
The Prentice position is an orientation of a prism, used in optics, optometry and ophthalmology. In this position, named after the optician Charles F. Prentice, the prism is oriented such that light enters it at an angle of 90° to the first surface, so that the beam does not refract at that surface. All the deviation caused by the prism takes ...