Wave Optics

Vocabulary practice flashcards covering wave theories of light, reflection, refraction, polarization, interference, diffraction, and optical instruments from the Wave Optics chapter.

Laws of Refraction

The rules governing the bending of light: (1) The incident ray, refracted ray, and the normal lie in the same plane. (2) The angle of incidence $i$ and angle of refraction $r$ satisfy Snell's law, n_1 \bind{\times} \text{or } n_1 \backslashsin(i) = n_2 \backslashsin(r), where $n_1$ and $n_2$ are absolute refractive indices.

Corpuscular Theory of Light

Newton's hypothesis proposing that light is made up of hard, elastic, and massless particles called corpuscles that travel in straight lines, where different colours correspond to different corpuscle sizes and speed increases in denser media due to attractive forces.

Wave Optics

The branch of optics that uses the wave nature of light to explain optical phenomena such as reflection, refraction, interference, diffraction, and polarization.

Ether (Huygens' Theory)

A hypothetical medium assumed by Huygens to be present everywhere, including in vacuum, through which light travels via the vibration of particles.

Primary Sources of Light

Sources that produce and emit light of their own due to high temperature, electric current passing through them, or chemical and nuclear reactions.

Secondary Sources of Light

Sources that do not produce light of their own, but instead receive light from an external source and reflect or scatter it around (such as the Moon, planets, and humans).

Wavefront

The locus of all points having the same phase of oscillation at a given instant of time. Rays of light are always perpendicular to the wavefront.

Plane Wavefront

A wavefront with flat, parallel surfaces obtained at points located far away from the source of light.

Huygens' Principle

The principle stating that each point on a wavefront acts as a secondary source emitting secondary wavelets in all directions at the speed of light, whose forward envelope forms the new wavefront.

Unpolarized Light

Light in which the electric field vectors vibrate in all possible directions perpendicular to the direction of propagation, with magnetic fields perpendicular to the electric fields.

Plane Polarized Light

Light in which the vibrations of the electric field vector are restricted to oscillate along one particular direction.

Polarizer

A material or device that allows light waves vibrating in one particular direction to pass through while blocking light waves vibrating in all other directions.

Polaroid

A type of synthetic plastic sheet used as a polarizer to produce plane polarized light.

Polarizing Axis

The specific transmission direction along which light waves (electric field vibrations) emerge from a polarizer.

Plane of Vibration

The plane containing the electric field vector of plane polarized light and the direction of propagation.

Plane of Polarization

The plane perpendicular to the plane of vibration in which no electric field vibrations take place.

Polarization

The phenomenon of converting unpolarized light into plane polarized light.

Malus' Law

A law stating that the transmitted intensity of a linearly polarized wave after passing through an analyzer is proportional to the square of the cosine of the angle between their polarizing axes: I_2 = I_1 \backslashcos^2(\theta).

Brewster's Law

A law stating that the tangent of the angle of incidence at which light is completely polarized upon reflection equals the ratio of the refractive indices of the two media: $\tan(\theta_B) = \frac{n_2}{n_1}$.

Brewster's Angle ($\theta_B$)

The particular angle of incidence at which the reflected light wave is completely plane polarized, the refracted wave is partially polarized, and the reflected and refracted rays are perpendicular ($\theta_B + \theta_r = 90^\circ$).

Interference of Light

The phenomenon in which the intensity of light is larger at some places and smaller at other places as a result of the superposition of two or more light waves.

Constructive Interference

Superposition occurring at points where the crest of one wave coincides with the crest of another (or trough with trough), resulting in maximum displacement and bright fringes.

Destructive Interference

Superposition occurring at points where the crest of one wave coincides with the trough of another, resulting in zero displacement and dark fringes.

Coherent Sources

Two sources that emit light waves of the same frequency having a constant or zero phase difference.

Fringe Width ($W$)

The distance between any two successive bright fringes or any two successive dark fringes, given by the formula $W = \frac{\lambda D}{d}$.

Lloyd's Mirror

A method for obtaining coherent sources where light from a single source reflects at a grazing angle off a plane mirror to form an interfering virtual source.

Fresnel Biprism

An optical device consisting of two prisms joined together with very small refracting angles ($30'$ to $1^\circ$) that splits light into two virtual coherent sources.

Optical Path Length

The distance in vacuum that light travels in the same time it takes to travel through a given distance in a medium, defined as $\text{Optical Path} = n \times d_{\text{medium}}$.

Diffraction of Light

The phenomenon in which light bends around the edges of obstacles or apertures in its path and enters regions where geometric shadows are expected.

Fraunhofer Diffraction

Diffraction that occurs when the source and screen are effectively at infinite distances from the obstacle or slit, using plane wavefronts and focusing lenses.

Fresnel Diffraction

Diffraction that occurs when the source and the screen are at finite distances from the diffracting obstacle or aperture, using spherical or cylindrical wavefronts without lenses.

Rayleigh's Criterion

The criterion stating that two point objects are just resolved when the central maximum of the diffraction pattern of one coincides with the first minimum of the diffraction pattern of the other.

Airy Disc and Airy Rings

The diffraction pattern produced by a circular aperture, comprising a central bright circular disc (Airy disc) surrounded by alternate dark and bright concentric circular rings (Airy rings).

Limit of Resolution

The minimum visual angle or linear separation between two point objects that allows them to be distinguished as separate by an optical instrument.

Resolving Power

The reciprocal of the limit of resolution, measuring the ability of an optical instrument to form separate, distinguishable images of closely spaced objects.

Numerical Aperture (N.A.)

A dimensionless number given by $n\sin(\alpha)$ that characterizes the range of angles over which an optical system can accept light, where $n$ is the refractive index and $\alpha$ is the half-angle of the light cone entering the objective.