This site is designed as a convenient location for visitors to view the various Java tutorials that have been constructed to aid in the understanding of concepts in light and color.

Electromagnetic Radiation - Electromagnetic radiation, the larger family of wave-like phenomena to which visible light belongs (also known as radiant energy), is the primary vehicle transporting energy through the vast reaches of the universe. This interactive tutorial explores the classical representation of an electromagnetic wave as a sine function, and enables the visitor to vary amplitude and wavelength to demonstrate how this function appears in three dimensions.

Electron Excitation and Emission - Electrons can absorb energy from external sources, such as lasers, arc-discharge lamps, and tungsten-halogen bulbs, and be promoted to higher energy levels. This tutorial explores how photon energy is absorbed by an electron to elevate it into a higher energy level and how the energy can subsequently be released, in the form of a lower energy photon, when the electron falls back to the original ground state.

Jablonski Diagram - Fluorescence activity can be schematically illustrated with the classical Jablonski diagram, first proposed by Professor Alexander Jablonski in 1935 to describe absorption and emission of light. This tutorial explores how electrons in fluorophores are excited from the ground state into higher electronic energy states and the events that occur as these excited molecules emit photons and fall back into lower energy states.

Color Temperature - Investigate the apparent "color" of a virtual radiator (in this case, a black metal pot) as it is slowly heated through a wide temperature range by external energy. The concept of color temperature is based on the relationship between the temperature and radiation emitted by a theoretical standardized material, termed a black body radiator, cooled down to a state in which all molecular motion has ceased. Hypothetically, at cessation of all molecular motion, the temperature is described as being at absolute zero or 0 Kelvin, which is equal to -273 degrees Celsius.

Lasers - This tutorial simulates the discharge of a ruby laser with a xenon flash tube. Chromium atoms in the laser crystal are excited by a flash tube and emit photons that are reflected back and forth between two mirrors at the ends of the laser crystal. As the photons traverse the crystal, they stimulate the emission of additional photons until enough energy is available for a pulse of photons to break through the thinly mirrored end on the right of the laser crystal.

Reflection of Light - Reflection of light (and other forms of electromagnetic radiation) occurs when the waves encounter a surface or other boundary that does not absorb the energy of the radiation and bounces the waves away from the surface. This tutorial explores the incident and reflected angles of a single light wave impacting on a smooth surface.

Specular and Diffuse Reflection - The amount of light reflected by an object, and how it is reflected, is highly dependent upon the smoothness or texture of the surface. When surface imperfections are smaller than the wavelength of the incident light (as in the case of a mirror), virtually all of the light is reflected equally. However, in the real world most objects have convoluted surfaces that exhibit a diffuse reflection, with the incident light being reflected in all directions. This interactive tutorial explores how light waves are reflected by smooth and rough surfaces.

Concave Mirrors - Real Images - The concave mirror tutorial demonstrates reflection patterns generated by mirrors with concave surfaces. The size of the real image produced by the mirror alters with changes in the distance between the object and the mirror.

Concave Mirrors - Virtual Images - This concave mirror tutorial demonstrates virtual images generated by mirrors with concave surfaces. Changes in the distance between the object and the mirror results in an alteration of the size of the virtual image that is generated.

Convex Mirrors - The convex mirror applet demonstrates reflection patterns generated by this type of mirror. The visitor can adjust the position of the object with respect to the mirror to see how it affects the resulting image.

Refraction of Light - Refraction occurs as light passes from one medium to another only when there is a difference in the index of refraction between the two materials. The effects of refraction are responsible for a variety of familiar phenomena, such as the apparent bending of an object that is partially submerged in water and the mirages observed on a dry, sandy desert. The refraction of visible light is also an important characteristic of lenses that enables them to focus a beam of light onto a single point. This interactive tutorial explores how changes to the incident angle and refractive index differential between two dissimilar media affect the refraction angle of light at the interface.

Magnification with a Bi-Convex Lens - Single lenses capable of forming images (like the bi-convex lens) are useful in tools designed for simple magnification applications, such as magnifying glasses, eyeglasses, single-lens cameras, loupes, viewfinders, and contact lenses. This interactive tutorial explores how a simple bi-convex lens can be used to magnify an image.

Prism Refraction - This tutorial explores the effect of prism-induced refraction on visible light according to Snell's law. Both incident angle and beam thickness can be adjusted to observe their effect on the resultant refracted light.

Diffraction of Light - Several of the classical and most fundamental experiments that help explain diffraction of light were first conducted between the late seventeenth and early nineteenth centuries by Italian scientist Francesco Grimaldi, French scientist Augustin Fresnel, English physicist Thomas Young, and several other investigators. These experiments involve propagation of light waves though a very small slit (aperture), and demonstrate that when light passes through the slit, the physical size of the slit determines how the slit interacts with the light. This interactive tutorial explores the diffraction of a monochromatic light beam through a slit of variable aperture.

Polarization of Light - When light travels through a linear polarizing material, a selected vibration plane is passed by the polarizer, while electric field vectors vibrating in all other orientations are blocked. Linearly polarized light transmitted through a polarizer can be either passed or absorbed by a second polarizer, depending upon the electric vector transmission azimuth orientation of the second polarizing material. This tutorial explores the effect of rotating two polarizers on an incident beam of white light.

Brewster's Angle - Light that is reflected from the flat surface of a dielectric (or insulating) material is often partially polarized, with the electric vectors of the reflected light vibrating in a plane that is parallel to the surface of the material. Common examples of surfaces that reflect polarized light are undisturbed water, glass, sheet plastics, and highways. In these instances, light waves that have the electric field vectors parallel to the surface are reflected to a greater degree than those with different orientations. This tutorial demonstrates the polarization effect on light reflected at a specific angle (the Brewster angle) from a transparent medium.

Wave Interactions in Optical Interference - The classical method of describing interference includes presentations that depict the graphical recombination of two or more sinusoidal light waves in a plot of amplitude, wavelength, and relative phase displacement. In effect, when two waves are added together, the resulting wave has an amplitude value that is either increased through constructive interference, or diminished through destructive interference. This interactive tutorial illustrates the effect by considering a pair of light waves from the same source that are traveling together in parallel, but can be adjusted with respect to coherency (phase relationship), amplitude, and wavelength.

Thomas Young's Double Slit Experiment - In 1801, an English physicist named Thomas Young performed an experiment that strongly inferred the wave-like nature of light. Because he believed that light was composed of waves, Young reasoned that some type of interaction would occur when two light waves met. This interactive tutorial explores how coherent light waves interact when passed through two closely spaced slits.

Double Refraction (Birefringence) in Iceland Spar - The first clues to the existence of polarized light surfaced around 1669 when Erasmus Bartholin discovered that crystals of the mineral Iceland spar (more commonly referred to as calcite) produce a double image when objects are viewed through the crystals in transmitted light. This interactive tutorial simulates viewing of a ball-point pen and a line of text through a crystal of Iceland spar, producing a double image.

Birefringent Crystals in Polarized Light - In order to examine how birefringent anisotropic crystals interact with polarized light in an optical microscope, the properties of an individual, isolated crystal can be considered. The specimen material in this tutorial is a hypothetical tetragonal birefringent crystal having an optical axis oriented in a direction that is parallel to the long axis of the crystal. Light entering the crystal from the polarizer will be traveling perpendicular to the optical axis of the crystal, regardless of the crystal orientation with respect to the polarizer and analyzer transmission axes. The virtual microscope viewport presents the crystal as it would appear in the eyepieces of a microscope under crossed-polarized illumination as it is rotated around the microscope optical axis.

Primary Additive Colors - Light is perceived as white by humans when all three cone cell types of the eye are simultaneously stimulated by equal amounts of red, green, and blue light. Because the addition of these three colors yields white light, the colors red, green, and blue are termed the primary additive colors. This tutorial explores how the three primary additive colors interact with each other, either in pairs or all together.

Primary Subtractive Colors - The complementary colors (cyan, yellow, and magenta) are also commonly referred to as the primary subtractive colors because each can be formed by subtracting one of the primary additives (red, green, and blue) from white light. This tutorial explores how the three primary subtractive colors interact with each other, either in pairs or all together.

Color Filters - Examine how color filters operate to alter the apparent color of objects visualized under white light and monochromatic illumination. The tutorial enables visitors to drag and drop red, green, and blue virtual color filters over objects illuminated with either white light or light that has been previously filtered with one of the primary additive colors.

Color Separation - Pigments and dyes are responsible for most of the color that humans see in the real world. Books, magazines, signs, and billboards are printed with colored inks that create colors through the process of color subtraction. This interactive tutorial explores how individual subtractive primary colors can be separated from a full-color photograph, and then how they can be reassembled to create the original scene.

Absorption Filters - Absorption filters, commonly manufactured from dyed glass or pigmented gelatin resins, are one of the most widely used types of filter for brightfield and fluorescence microscopy. These filters operate by attenuation of light through absorption of specific wavelengths, so that spectral performance is a function of the physical thickness of the filter and the amount of dye present in the glass or gelatin matrix. This interactive tutorial explores how absorption filters pass certain wavelengths of light while blocking others.

Human Vision - The human vision interactive Java tutorial explores what happens in the human eye when an image is focused on the retina. The tutorial allows visitors to adjust the distance of an object from the eye to vary the size of the image.

Lens Shape - This tutorial explores the effect of lens shape on the interaction of a lens with light. The lens may be adjusted to produce a concave or convex surface, and the concepts of refraction, convergence, and divergence of light are considered.

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