Optics — 54 Terms Defined

Magnification Optics Dimensionless The ratio of image height to object height, or ratio of image distance to object distance in an optical system. m = h_image / h_object = -v / u

Malus's Law Optics W/m² The law stating that intensity of linearly polarized light transmitted through an analyzer is proportional to the squared cosine of the angle between polarizer and analyzer transmission axes. I = I0 cos² θ

Michelson Interferometer Optics m An optical instrument that splits a beam of light into two perpendicular paths and recombines them to create high-precision interference fringes. 2 d = m λ

Minimum Deviation Optics Degrees (°) The minimum value of deviation angle achieved when light passes symmetrically through a triangular prism. n = sin[(A + δ_m)/2] / sin(A/2)

Mirage Optics N/A An optical illusion caused by continuous refraction of light rays passing through air layers with steep temperature and density gradients. n(z) = f(Temperature gradient)

Near Point & Far Point Optics m (or cm) The closest and farthest distances at which the human eye can focus objects sharply on the retina. Near Point ≈ 25 cm (Normal adult eye), Far Point = ∞

Newton's Rings Optics m An interference pattern of concentric bright and dark rings formed by an air film enclosed between a plano-convex lens and a flat glass plate. r_m² = m λ R (Dark rings in reflection)

Optical Axis Optics N/A The imaginary central straight line passing through the centers of curvature of all optical elements in a rotationally symmetric system. N/A

Optical Fiber Optics dB/km A flexible, transparent glass or plastic fiber that transmits light signals across long distances via total internal reflection. NA = √(n_core² - n_cladding²)

Optical Power Optics Diopters (D, m⁻¹) A measure of a lens or curved mirror's degree of light convergence or divergence, equal to the reciprocal of its focal length. P = 1 / f (in meters)

Paraxial Approximation Optics rad (radians) A small-angle approximation in geometric optics assuming light rays make small angles $Î¸$ with the optical axis. sin θ ≈ θ, tan θ ≈ θ, cos θ ≈ 1

Polarization Optics N/A The property of transverse electromagnetic waves specifying the geometric orientation of their electric field vector oscillations in space. E(z,t) = E0 cos(k z - ω t) i_hat

Presbyopia Optics Diopters (D) The age-related loss of accommodation power in the human eye caused by reduced elasticity of the crystalline lens. Near Point > 25 cm (increases with age)

Rainbow Formation Optics Degrees (°) An optical meteorological phenomenon caused by reflection, refraction, and chromatic dispersion of sunlight inside raindrops. θ_primary ≈ 42° (Red outer, violet inner)

Rayleigh Criterion Optics rad (radians) The condition for two point sources to be barely resolved by an optical instrument, stating that the central diffraction maximum of one image coincides with the first minimum of the other. θ_min = 1.22 λ / D

Rayleigh Scattering Optics W/m² The elastic scattering of light or electromagnetic radiation by particles much smaller than the light's wavelength. I_scattered ∝ 1 / λ⁴

Real Image Optics m An optical image formed by actual convergence of light rays, which can be projected onto a physical screen. v > 0 (for real image), m < 0 (inverted)

Reflection Optics Degrees (°) The bouncing back of a light ray or wave when it strikes a boundary surface between two different media without entering the second medium. θ_i = θ_r

Refraction Optics Dimensionless (n) The bending of a light ray as it passes obliquely from one transparent medium into another with a different refractive index. n1 sin θ1 = n2 sin θ2 (Snell's Law)

Resolving Power Optics Dimensionless The ability of an optical instrument or grating to separate and distinguish two closely spaced point objects or adjacent spectral wavelengths. R = λ / Δλ = N m (Grating), RP = 1 / Δθ

Simple Microscope Optics Dimensionless (×) An optical magnifying instrument consisting of a single converging biconvex lens used to produce an enlarged, upright, virtual image. M = 1 + (D / f) (Image at near point D)

Spherical Aberration Optics m An image blur defect in spherical lenses and mirrors where marginal rays focus closer to the element than paraxial central rays. Δf_spherical = f_marginal - f_paraxial

Spherical Mirror Optics m A curved mirror having a reflective surface shaped like a section of a sphere, classified as concave (converging) or convex (diverging). 1/f = 1/v + 1/u, f = R/2

Terrestrial Telescope Optics Dimensionless (×) A refracting telescope incorporating an additional erecting lens system between objective and eyepiece to yield an upright image for ground observation. M = f_obj / f_eye, Tube Length L = f_obj + 4 f_erect + f_eye