page_title: Compact fluorescent lamp
section_title: Spectrum of light
hierarchical_section_title: Compact fluorescent lamp / Characteristics / Spectrum of light
caption_attribution_description: English: A very basic spectroscope made from a slit in cardboard and a prism. Even a simple instrument like this reveals a clear difference in the visible spectrum of an incandescent lamp and an arc-discharge–based low-energy-consumption lamp.
context_page_description: A compact fluorescent lamp, also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube which is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.
  Compared to general-service incandescent lamps giving the same amount of visible light, CFLs use one-fifth to one-third the electric power, and last eight to fifteen times longer. A CFL has a higher purchase price than an incandescent lamp, but can save over five times its purchase price in electricity costs over the lamp's lifetime. Like all fluorescent lamps, CFLs contain toxic mercury which complicates their disposal. In many countries, governments have banned the disposal of CFLs together with regular garbage. These countries have established special collection systems for CFLs and other hazardous waste.
context_section_description: CFLs emit light from a mix of phosphors, each emitting one band of color with some bands still in the ultraviolet range as can be seen on the light spectrum.  Modern phosphor designs balance the emitted light color, energy efficiency, and cost. Every extra phosphor added to the coating mix improves color rendering but decreases efficiency and increases cost. Good quality consumer CFLs use three or four phosphors to achieve a "white" light with a color rendering index (CRI) of about 80, where the maximum 100 represents the appearance of colors under daylight or other sources of black-body radiation such as an incandescent light bulb (depending on the correlated color temperature).
  Color temperature can be indicated in kelvins or mireds (1 million divided by the color temperature in kelvins). The color temperature of a light source is the temperature of a black body that has the same chromaticity (i.e. color) as the light source. A notional temperature, the correlated color temperature, the temperature of a black body which emits light of a hue which to human color perception most closely matches the light from the lamp, is assigned.
  The color temperature is characteristic of black-body radiation; practical white light sources approximate the radiation of a black body at a given temperature, but will not have an identical spectrum. In particular, narrow bands of shorter-wavelength radiation are usually present even for lamps of low color temperature ("warm" light).
  As color temperature increases, the shading of the white light changes from red to yellow to white to blue. Color names used for modern CFLs and other tri-phosphor lamps vary between manufacturers, unlike the standardized names used with older halophosphate fluorescent lamps. For example, Sylvania's Daylight CFLs have a color temperature of 3500 K, while most other lamps called daylight have color temperatures of at least 5000 K. In United States, Energy Star's specification provides a set of named color temperatures for certified luminaries.
caption: Emitted visible light spectrum of an incandescent lamp (mid) and a CFL (bottom)
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