PROPERTIES OF LIGHT

                                   What we perceive as 'light", or different colors, could be a narrow band within the spectrum. some of the opposite frequency bands within this spectrum are called radio waves, microwaves, infrared waves, and X-rays. Picture the approximate frequency ranges for a few of the electromagnetic bands.

Each frequency value within the visible band corresponds to a definite color. At the low-frequency end could be a red color (4.3 X 10" hertz), and therefore the highest frequency we will see could be a violet color (7.5 X 10" hertz). coloring range from the reds through orange and yellow at the low-frequency end to greens, blues, and violet at the high end
Since light is an nonparticulate radiation, we will describe the assorted colors in terms of either the frequency for the wavelength λ of the wave, we illustrate the oscillations present during a monochromatic nonparticulate radiation, polarized so the electrical oscillations are in one plane. The wavelength and frequency of the monochromatic wave are inversely proportional to every other, with the proportionality constant because the speed of sunshine c:

                               C = λf

Frequency is constant for all materials, but the speed of sunshine and therefore the wavelength are material-dependent. during a vacuum, c = 3 x 101•‹ cm/sec. Light wavelengths are very small, so length units for designating spectral colors are usually either angstroms (1Ao = l0-8 cm) or nanometers (1 nm = l0-7 cm) identical term for nanometer is millimicron. Light at the red end of the spectrum features a wave length of roughly 700 nanometers (nm), and therefore the wavelength of the violet light at the opposite end of the spectrum is about 400 nm. Since wavelength units are somewhat more convenient to handle than frequency units, spectral colors are typically per terms of wavelength.

A light source like the sun or a lightweight bulb emits all frequencies within the visible range to supply white light. When white light is incident upon an object, some frequencies are reflected and a few are absorbed by the article. the mixture of frequencies present within the reflected light determines what we perceive because the color of the article. If low frequencies are predominant within the reflected light, the article is described as red. during this case, we are saying the perceived light features a dominant frequency (or dominant wavelength) at the red end of the spectrum. The dominant frequency is additionally called the hue, or just the colour, of the sunshine.

Other properties besides frequency are needed to explain the assorted characteristics of sunshine. once we view a source of sunshine, our eves answer the colour (or dominant frequency) and two other basic sensations one in every of these we call the brightness, which is that the perceived intensity of the sunshine. Intensity is that the energy emitted per unit time, per unit angle, and p:r unit projected area of the source. energy is said to the luminance of the source. The second perceived characteristic is that the purity, or saturation, of the sunshine. Purity describes how washed out or how "pure" the colour of the sunshine appears. Pastels and pale colors are described as less pure. These three characteristics, dominant frequency, brightness, and purity, are commonly wont to describe the various properties we perceive during a source of sunshine. The term chromaticity is employed to refer collectively to the 2 properties describing color characteristics: purity and dominant frequency.

Energy emitted by a white-light source features a distribution over the visible frequencies. Each frequency component within the range from red to violet contributes more or less equally to the whole energy, and therefore the color of the source is described as white. When a dominant frequency is present, the energy distribution for the source takes a form. we'd now describe the sunshine as having the colour love the dominant frequency. The energy density of the dominant light component is labeled as ED during this figure, and therefore the contributions from the opposite frequencies produce white light of energy density Ew we will calculate the brightness of the source because the area under the curve, which provides the whole energy density emitted. Purity depends on the difference between ED and Ew. The larger the energy ED of the dominant frequency compared to the white-light component Ew, the more pure the sunshine. we've got a purity of 100% when Ew = 0 and a purity of 0 percent when Ew, = ED.

When we view light that has been formed by a mix of two or more sources, we see a resultant light with characteristics determined by the first sources. Two different-color light sources with suitably chosen intensities may be wont to produce a variety of other colors. If the 2 color sources combine to supply white light, they're mentioned as complementary colors. samples of complementary pairs are red and cyan, green and magenta, and blue and yellow. With a judicious choice of two or more starting colors, we will form a good range of other colors. Typically, color models that are wont to describe combinations of sunshine in terms of dominant frequency (hue) use three colors to get a fairly wide selection of colours, called the colour gamut for that model. the 2 or three colors wont to produce other colors in such a color model are mentioned as primary colors.

Thus, an RGB color monitor cannot display colors within the neighborhood of 500 nm.