Photonics Midterm Definitions

Light Ray

A line representing the direction in which light energy flows

Ray Model of Light

A model that treats light as rays travelling along paths; useful for mirrors, lenses, prisms, reflection, and refraction

Ray Approximation

Treating light as rays when the wavelength is much smaller than the relevant object or opening size: wavelength«d

Wavefront

A surface containing points of a wave that have the same phase

Electromagnetic wave

A wave consisting of oscillating electric and magnetic fields

Wavelength

The distance over which a wave repeats, such as distance between two consecutive crests

Frequency

The number of complete wave cycles occurring each second, measured in hertz (Hz)

Period

The time required for one complete oscillation T=1/f

Amplitude

The maximum magnitude of a wave’s oscillation

Angular Frequency

The rate at which the phase of a wave changes: w=2*pi*f

Wave vector k

A vector pointing in the direction of the wave propagation whose magnitude is k=2pi/wavelength

Phase

Described where a wave its within its oscillation cycle

Phase Difference

The difference in phase between two waved or two points on a wave

Intensity

The power carried by light per unit area I=P/A

Energy Density u

The amount of electromagnetic energy contained per unit volume

Radiation Pressure

Pressure produced when electromagnetic radiation transfers momentum to a surface

Photon Energy

The discrete energy associated with absorption or emission at a particular frequency E=hf=hc/wavelength

Dispersion

The separation of light by wavelength because different wavelengths undergo different amounts of refraction

Chromatic Aberration

An optical effect in which different wavelengths focus at different locations because refractive index depends on wavelength

Corpuscular Theory of Light

Newtons proposal that light consists of tiny particles called corpuscles

Energy Quantization

The idea that energy can occur in discrete amounts rather than arbitrary continuous values, E=0, hf, 2hf, 3hf

Reflection

Light returning into its original medium after reaching a boundary

Refraction

The change in direction of light when it passes from one medium into another

Index of refraction n

A measure relating the speed of light in vacuum to its speed in a material n=c/v

Normal

An imaginary line perpendicular to a surface at the point where the light ray strikes it

Critical Angle (theta c)

The angle of incidence in the higher-index medium that. produces a refracted angle of 90 degrees

Total Internal Reflection (TIR)

complete reflection of light when it travels