Close examination of the visible-light spectrum from our Sun and other stars reveals a pattern of dark lines—called absorption lines. These patterns can provide important scientific clues that reveal hidden properties of objects throughout the universe. Certain elements in the Sun's atmosphere absorb certain colors of light. These patterns of lines within spectra act like fingerprints for atoms and molecules. Looking at the Sun's spectrum, for example, the fingerprints for elements are clear to those knowledgeable about those patterns.

As the full spectrum of visible light travels through a prism, the wavelengths separate into the colors of the rainbow because each color is a different wavelength. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers.

Epi-illumination

Adjust the diopters on the microscope eyepieces to zero. Adjust the interpupillary distance of both eyepieces to fit your eyes.

The last step is to adjust the condenser aperture iris to match the NA (numerical aperture) indicated on the objective. The aperture iris can also be stopped down to 60% of the NA setting (trading image resolution for contrast.) An alternative way to set the condenser aperture is to remove the eyepiece and look down the eye tube at the back of the objective and adjust the aperture diaphragm until approximately 90% of the area is illuminated (a setting that visually looks very near the edge of the objective but is not quite fully to the edge).

Determine which objective will be used most for your detailed work. It is recommended that you start with a 10X. This will be the target objective for aligning the Koehler illumination. For publication images, the Koehler illumination should be set for each objective used to photograph specimens.

All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light. Cone-shaped cells in our eyes act as receivers tuned to the wavelengths in this narrow band of the spectrum. Other portions of the spectrum have wavelengths too large or too small and energetic for the biological limitations of our perception.

National Aeronautics and Space Administration, Science Mission Directorate. (2010). Visible Light. Retrieved [insert date - e.g. August 10, 2016], from NASA Science website: http://science.nasa.gov/ems/09_visiblelight

Science Mission Directorate. "Visible Light" NASA Science. 2010. National Aeronautics and Space Administration. [insert date - e.g. 10 Aug. 2016] http://science.nasa.gov/ems/09_visiblelight

The visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view. More simply, this range of wavelengths is called visible light. Typically, the human eye can detect wavelengths from 380 to 700 nanometers.

In order to set up a microscope for Koehler illumination, the microscope has to have a vertically adjustable, centerable condenser and field diaphragm as illustrated in the figure below.

Koehler illumination is a microscope technique that provides superior control over the light rays during brightfield microscopy by aligning and focusing the microscope, ensuring the best resolution and contrast, as well as a bright, evenly illuminated background for your images. Koehler illumination is critical for the following advanced contrasting techniques: Phase contrast, Varel contrast, Hoffman Modulation, PlasDIC and DIC. Prior to setting up and aligning the advanced contrasting components, the microscope’s Koehler illumination must be aligned.

NASA’s Juno spacecraft entered orbit around Jupiter in 2016, the first explorer to peer below the planet's dense clouds to…

The Sun is the dominant source for visible-light waves our eyes receive. The outer-most layer of the Sun's atmosphere, the corona, can be seen in visible light. But it is so faint it cannot not be seen except during a total solar eclipse because the bright photosphere overwhelms it. The photograph below was taken during a total eclipse of the Sun where the photosphere and chromosphere are almost completely blocked by the moon. The tapered patterns—coronal streamers—around the Sun are formed by the outward flow of plasma that is shaped by magnetic field lines extending millions of miles into space.

科勒照明

Laser altimeters can also make unique measurements of the heights and characteristics of clouds, as well as the top and structure of the vegetation canopy of forests. They can also sense the distribution of aerosols from sources such as dust storms and forest fires.

Our Sun produces more yellow light than any other color because its surface temperature is 5,500°C. If the Sun's surface were cooler—say 3,000°C—it would look reddish, like the star Betelgeuse. If the Sun were hotter—say, 12,000°C—it would look blue, like the star Rigel.

Isaac Newton's experiment in 1665 showed that a prism bends visible light and that each color refracts at a slightly different angle depending on the wavelength of the color.

Place a sample slide on the stage and bring it into focus with the selected target objective (it may be helpful to start by focusing with a lower magnification objective and then stepping up to the target objective). You may have to adjust the opening of the field diaphragm to get an edge into the field of view (this condenser focus point tends to be near the specimen end of the condenser focus travel).

Laser altimetry is an example of active remote sensing using visible light. NASA's Geoscience Laser Altimeter System (GLAS) instrument onboard the Ice, Cloud, and land Elevation Satellite (ICESat) enabled scientists to calculate the elevation of Earth's polar ice sheets using lasers and ancillary data. Changes in elevation over time help to estimate variations in the amount of water stored as ice on our planet. The image below shows elevation data over the West Antarctic Ice Streams.

NASA explores the unknown in air and space, innovates for the benefit of humanity, and inspires the world through discovery.

Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…

Gradually open the field iris and make final tweaks of the centration with the field iris at the very edge of the field of view. Then open the field iris just outside the field of view.

As objects grow hotter, they radiate energy dominated by shorter wavelengths, changing color before our eyes. A flame on a blow torch shifts from reddish to bluish in color as it is adjusted to burn hotter. In the same way, the color of stars tells scientists about their temperature.

Patterns are also evident in a graph of an object's reflectance. Elements, molecules, and even cell structures have unique signatures of reflectance. A graph of an object's reflectance across a spectrum is called a spectral signature. Spectral signatures of different Earth features within the visible light spectrum ARE shown below.