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See also: principle, rule, theorem.
SciSpeak A uniform principle or constant
lawA uniform principle or constant. See Boyle's law, Charles' law, Farr's law of epidemics, Fick's law of diffusion, Frank-Starling law, Gown's law, Gresham's law, Hardy-Weinberg law, Harvard law, Heart law, Leborgne's law, Moore's law, Murphy's law of genetics, Natural law, Natural sexual law, Ohm's law, Periodic law, Roemer's law, Sutton's law, Talion law Government A legislative act that compels compliance. See AIDS disclosure law, Annie's law, Anti-dumping law, Antikickback law, Antisubstitution law, Antitrust law, Baby Doe law, Bad baby law, Chinese Law on Maternal & Infant Health Care law, Company doctor law, Due process law, Good Samaritan law, Heart law, Megan's law, Preemptive tobacco control law, Prompt payment law, Roemer's law, Seat belt law, Son of Sam law, Stark law, Sunset law.
See also: principle, rule, theorem
Abney's law The total luminance of an area is equal to the sum of the luminances that compose it.
Alexander's law An increase in the intensity of a jerk nystagmus when the eyes move in the direction of the fast phase.
all or none law The response in a nerve fibre to any stimulus strong enough to produce a response is always of the same amplitude. However, different nerve fibres have action potentials with different amplitudes. An increase in the intensity of the stimulus yields only an increase in the frequency of nerve impulses (or action potentials). Syn. all or nothing law.
Aubert-Förster law See Aubert-Förster phenomenon.
Bloch's law The luminance L of a stimulus required to produce a threshold response is inversely proportional to the duration of exposure t of the stimulus, i.e.
Bunsen-Roscoe law In photochemistry, the product of the intensity of the light stimulus and the duration of exposure is a constant. Syn. law of reciprocity.
cosine law See diffusion.
Descartes' law See law of refraction.
Donders' law For any determinate position of the line of fixation with respect to the head there corresponds a definite and invariable angle of torsion.
Draper's law An effect is produced in a medium only by that portion of the spectrum which is absorbed by the medium. The effect may be thermal, chemical or the production of fluorescence. Syn. Grotthus' law.
Emmert's law The apparent size of a projected after-image varies in proportion to the distance of the surface on which it is projected. The law can be expressed by the following relationship h/H = d/D, where h is the linear size of the object, H the apparent size of the projected after-image, d the object's distance from the observer and D the distance between the observer and the surface on which the after-image is projected. It follows from the above expression that H = hD/d, i.e. the greater the distance of the projected image the larger its apparent size.l. of equal innervation See Hering's law of equal innervation.
Fechner's law The intensity of a sensation S varies as the logarithm of the intensity I of the stimulus, i.e.
Fermat's law The path taken by a light ray in going from one point to another is that route which takes the least time. Syn. Fermat's principle.
Ferry-Porter law The critical flicker frequency F is directly proportional to the logarithm of the luminance L of the stimulus, i.e.
Granit-Harper law The critical fusion frequency increases with the logarithm of the retinal area stimulated.
Grassmann's law's Laws of colour mixture. 1. The first law states that any colour C of the visible spectrum can be matched in appearance by a mixture of three primary colours, such as red R, green G and blue B, provided that none of these can be matched by a mixture of the other two, i.e.
Grotthus' law See Draper's law.
Helmholtz's law of magnification See Lagrange's law.
Hering's law of equal innervation Innervation to the extraocular muscles is equal to both eyes. Thus, all movements of the two eyes are equal and symmetrical. Syn. Hering's law; law of equal innervation. See yoke muscles.
law of identical visual directions An object stimulating corresponding retinal points is localized in the same apparent monocular direction in each eye. Syn. law of oculocentric visual direction. See line of direction; retinal corresponding points.
inverse square law of illumination The illuminance E of a surface by a point source is directly proportional to the luminous intensity I of a point source and to the cosine of the angle θ of incidence and inversely proportional to the square of the distance d between the surface and the source, i.e.
Imbert-Fick law Applied to applanation tonometry, this law states that the intraocular pressure P (in mmHg) is equal to the tonometer weight W (in g) divided by the applanated area A (in mm2), hence,
Kirschmann's law The greatest contrast in colour is seen when the luminosity difference is small.
Knapp's law A correcting lens placed at the anterior focal plane of an axially ametropic eye forms an image equal in size to that formed in a standard emmetropic eye. Knapp's law applies to the relative spectacle magnification but not to the spectacle magnification. Syn. Knapp's rule.
Kollner's law See Kollner's rule.
Lagrange's law In paraxial optics, the product of the index of refraction of image space n′, the image size h′ and the half-angle of the refracted cone in image space u′ is equal to the product of the index of refraction of object space n, the object size h and the half-angle of the incident cone in object space u, i.e.
Lambert's law See diffusion.
Listing's law When an eye moves to any position from the primary position, it may be considered to have made a single rotation about an axis that is perpendicular to both the initial and final lines of fixation at their point of intersection.
law of oculocentric visual direction See law of identical visual directions.
Piéron's law See Ricco's law.
Piper's law See Ricco's law.
Planck's law Law giving the energy distribution of a black body as a function of wavelength, for a specified temperature.
power law See Fechner's law.
Prentice's law The prismatic effect P in prism dioptres at a point on a lens is equal to the product of the distance c in centimetres of the point from the optical centre of the lens, and the dioptric power F of the lens, i.e.
law of reciprocity See Bunsen-Roscoe law.
law of reflection The incident and reflected rays and the normal to the surface at the point of incidence lie in the same plane and the angle of incidence is equal to the angle of reflection (Fig. L5).
law of refraction The incident and refracted rays and the normal to the surface at the point of incidence lie in the same plane and the ratio of the sine of the angle of incidence i to the sine of the angle of refraction i′ is a constant for any two media, i.e.
Ricco's law The product of the absolute threshold of luminance L and the image area A is a constant, i.e.
Sherrington's law of reciprocal innervation The contraction of a muscle is accompanied by simultaneous and proportional relaxation of its antagonist. For example, if the superior oblique muscle contracts, its antagonist, the inferior oblique muscle, relaxes. The validity of this law has been established by electromyography.
Smith-Helmholtz law See Lagrange's law.
Snell's law See law of refraction.
Stevens' law See Fechner's law.
Talbot's law See Talbot-Plateau law.
Talbot-Plateau law The brightness of a light source presented at short intervals above the critical fusion frequency is equal to that which would be produced by a constant light source of an intensity equal to the mean value of the intermittent stimuli. Syn. Talbot's law.
Weber's law The just noticeable difference (or difference threshold) in intensity of a stimulus ΧI varies as a constant ratio of the initial intensity of the stimulus I, i.e.
Weber-Fechner law See Weber's law.
|Table L1 Approximate amount of spectacle lens decentration (in mm) of its optical centre away from the pupillary centre of the eye to produce five prismatic effects (in prism dioptres) for distance vision. The results ignore the effect of spherical aberration|
|lens power + or −||prismatic effect required|
|1 Χ||2 Χ||3 Χ||4 Χ||5 Χ|
Patient discussion about law
Q. Mother in law not accepting the diagnosis. Our 3 years old son was diagnosed with autism some time ago, and although it’s not easy, our family and friends support and help us a lot, except my mother in-law (that lives close to us). She refuse to accept the fact that our son has autism, and keeps telling we are just hysteric and with little education our child will grow up just fine. What can we do? Were we wrong when we decided to tell everyone?
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