OPTICS 101 Exam 1 Vocab

These are crucial for the exam

Absorption

The process in which a propagating wave loses optical power or irradiance as it travels through a material, with the energy being absorbed by the material. This energy can be converted into electronic or thermal energy.

Angular Size

the angle formed by the rays from opposite edges of the object that pass through the center of the aperture stop (chief rays). It represents the apparent size of the object as seen through the optical system.

Dispersion

The change in speed of a wave as its frequency or wavelength changes. It is usually described by how the refractive index changes with wavelength.

Irradiance

The optical power carried by a beam per unit area. It describes how much optical power falls on a surface, such as a sensor or solar cell.

Magnification

In an imaging system, its the ratio of the image’s size to the object’s size, measured across the image and object.

Material Dispersion

The variation of refractive index/phase velocity with frequency (or wavelength) caused by particular microscopic properties of an optical material.

Phase

An angular measure of the fractional shift of a harmonic wave.

Phase Velocity

The speed at which a wave front travels (propagates) through space

Planck’s Constant

The constant of proportionality relating the photon energy to its frequency.

E = hv

h = 6.626 * 10^-34

Radiant Intensity

the amount of light or other electromagnetic power a source emits in a specific direction per unit solid angle. Power per unit solid angle measured at a distance much larger than the size of the source.

Scattering

light changes direction because it encounters irregularities or particles in a material. It can be predictable, like with a diffraction grating, or random, like with particles in the atmosphere.

Solid Angle

Solid angle measures how much of a 3D space an object appears to cover when viewed from a point. It is measured in steradians (sr).

For a small object, the solid angle is approximately:

Solid angle = cross-sectional area / distance ^2

Spectral Density

describes how energy, power, or irradiance is distributed across different wavelengths or frequencies. For example, irradiance spectral density can be measured in watts per square meter per nanometer (W/m²/nm).

Standing Wave

a wave that does not move through space. Instead, it oscillates in place with a fixed pattern. In optics, it can be formed when two waves travel in opposite directions and interfere.

Traveling Wave

a disturbance that moves through space without changing its shape. It usually travels at a constant speed.

Wavelength

The period of oscillation (in space) of a harmonic wave.

Photon

An elementary particle of light and other electromagnetic radiation. A photon carries energy proportional to the optical frequency and has zero rest mass.