Section Overview:
Light is a complex phenomenon that is classically explained with a simple model based on rays and wavefronts. The Olympus Microscopy Resource Center Microscopy Primer explores many of the aspects of visible light starting with an introduction to electromagnetic radiation and continuing through to human vision and the perception of color. Each section outlined below is an independent treatise on a limited aspect of light and color. We hope you enjoy your visit and find the answers to your questions.
Review Articles
Electromagnetic Radiation
Electromagnetic radiation, the larger family of wave-like phenomena to which visible light belongs, is the primary vehicle transporting energy through the vast reaches of the universe.
Light: Particle or a Wave?
Scientists have attempted to explain how electromagnetic radiation can display duality, or both particle-like and wave-like behavior. At times light behaves as if composed of particles, and at other times as a continuous wave.
Sources of Visible Light
A variety of sources are responsible for emission of electromagnetic radiation, and are generally categorized according to the specific spectrum of wavelengths generated by the source.
Fluorescence
Fluorescence microscopy studies material that can be made to fluoresce, either in its natural form (primary or auto fluorescence) or when treated with chemicals capable of fluorescing (secondary fluorescence).
Speed of Light
In 1983, the speed of light was defined as being 299,792.458 kilometers per second by the Seventeenth General Congress on Weights & Measures. Generally, it is rounded to 300,000 kilometers per second.
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.
Refraction of Light
Scientists realized that the ratio between the angle at which light crosses the media interface and the angle produced after refraction is a precise characteristic of the material producing the refraction effect.
Diffraction of Light
Diffraction of light occurs when a light wave passes by a corner or through an opening or slit that is physically the approximate size of, or even smaller than, that light's wavelength.
Polarization of Light
Sunlight and artificial illumination transmit light waves whose electric field vectors vibrate in all perpendicular planes to the direction of propagation. When the electric field vectors are restricted to a single plane by filtration, light is said to be polarized.
Interference
An important characteristic of light waves is their ability, to interfere with one another. A great example of interference is when light is reflected from film of oil floating on water or a soap bubble, which reflects a variety of beautiful colors when illuminated by a light source.
Optical Birefringence
When light enters a non-equivalent axis in an anisotropic crystal, it is refracted into two rays each polarized with the vibration directions oriented at right angles to one another, and traveling at different velocities. This phenomenon is termed birefringence.
Color Temperature
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.
Primary Colors
The human eye is sensitive to a band of electromagnetic radiation that lies in the wavelength range between 400 and 700 nanometers, known as the visible light spectrum. Red, green, and blue are considered the primary colors because they are fundamental to human vision.
Light Filtration
It is often desirable to produce light that has a restricted wavelength spectrum. This can be easily accomplished through the use of specialized filters that transmit some wavelengths and selectively absorb or reflect unwanted wavelengths.
Human Vision and Color Perception
Human vision involves the nearly simultaneous interaction of the two eyes and the brain through a network of neurons, receptors, and other specialized cells, with the stimulation of light receptors in the eyes.
Light and Energy
Examine the relationship between light and energy as mankind has always been dependent upon energy from the sun's light both directly - for warmth, to dry clothing, to cook, and indirectly to provide food, water, and air.
Lenses and Geometrical Optics
The concepts explored in this discussion, which are derived from the science of Geometrical Optics, will lead to an understanding of the magnification process, the properties of real and virtual images, and lens aberrations.
Basic Properties of Mirrors
Mirrors of different design and construction vary widely in their reflectivity, from nearly 100 percent for highly-polished mirrors coated with metals that reflect visible and infrared wavelengths, to zero for strongly absorbing materials.
Prisms and Beamsplitters
Prisms (polished blocks of glass or other transparent materials) and beamsplitters are components that bend, split, reflect, and fold light through the pathways of both simple and sophisticated optical systems.
Laser Fundamentals
Lasers are designed to produce and amplify this stimulated form of light into intense and focused beams. The word laser was coined as an acronym for Light Amplification by the Stimulated Emission of Radiation.
Light and Color Interactive Tutorials
Difficult concepts in the physics of light and the science of optics are much easier to understand with the aid of interactive java tutorials that demonstrate various aspects of the principles involved.